How can the X chromosome help with maternal versus paternal?

“My half-sister and I have been tested to confirm half-siblings. Is there any way to know which parent we share” – this is a rephrasing of a question posed by a woman on the DNA-ADOPTION mailing list at Yahoo. A discussion of the problems of mtDNA ensued. Because the mtDNA haplogroups go back thousands of years, a match is no guarantee of a recent ancestor like a mother. So that information can only rule out the maternal side if there is a mismatch. Deeper mtDNA can get closer but still this is not certain territory yet.

However since they are both female, the X chromosome can give a definitive answer because their father(s) would pass his only X chromosome unchanged to each of them. A man has one X and one Y chromosome and a woman has two X chromosomes. Whether the father passes an X or a Y to his child determines its sex, but since neither is recombined the child gets exactly the same X or Y chromosome as the dad has.

Since a girl has two X chromosomes, one is from her dad. Two sisters with the same dad will therefore ALWAYS match on the entire X chromosome since they have one complete X in common.  If the mothers are related, then some of their X will be a full match as well. So let’s look at some X chromosome comparisons at GEDmatch:

Two Half Sisters X comparison at Gedmatch

This is what the two half sisters from the question look like. The blue indicates that there is a match, the colors above it whether on one chromosome (yellow) or both (green), while red is no match. A few small errors can creep in when processing DNA so an occasional little red line can be from an error. Click the read more once you have decided if they have the same mother or the same father.



That’s right, the same mother. If they had the same father you would see a solid blue line as shown below in the made-up example of two half sisters with the same father.

Two Half Sisters X same Dad

And here are two full sisters with the same parents, my maternal aunts:

Two Half Sisters X same Dad

Here is the 23andme view of my aunts using “Family Traits” from under “Family and Friends,” the black is full identical and blue is half identical (so father’s side only):


So can two half brothers tell which side? Yes to some extent. They would expect half matching X if they have the same mother but it can vary widely. If they have no matching X except at the very beginning of that chromosome (see below), then they probably have the same Dad, but that is much easier to tell by just looking at the Y chromosome for each of them.

Here are two full brothers, half brothers with the same mother would look very similar to this as well:


How about a half brother and a half sister? If they have no matching X then they probably have the same Dad, but unlike sisters this is by no means a sure thing. On the other hand, if they have about 30-70% matching X then they probably have the same mother or their mothers could be related. Test a few more people if you can.

Here is a full sister and a full brother, again half related maternally would look very much like this:

SistervBrother and another full brother and sister (me and my brother):


Notice how the beginning of the X is grayed out on the 23andme diagram above? That is actually where the X and Y do a little recombination after all, which we generally ignore for simplicity. Here is the X of my brother versus my Dad at GEDmatch to illustrate that:


Another way you can see this is to browse the raw data for a man at 23andme or in a spreadsheet and notice that there are two letters for every position at the beginning of the X chromosome until you reach “Browsing SNPs on Chromosome X: positions 2630381 through 2715425 out of 1552705” where you start to get only one.

Here is a delightful article about X inheritance or why your braininess may come from your mother:

UPDATE 16 Apr 2017: A reader asked in the comment how a mother daughter X would look so here is an example:

UPDATE 10 Feb 2019: In the new Gedmatch all X comparisons will have a small break In the middle. Check the box at the bottom of the form that says Prevent Hard Breaks (etc) to get rid of that little black box.


370 thoughts on “How can the X chromosome help with maternal versus paternal?

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  1. I love reading about all these people who have not only themselves tested, but siblings and other close kinfolk. Sadly, my sister IS NOT INTERSTED in any of this genealogy, DNA genealogy and related study. So reading this is great and FRUSTRATING! Our parents are long gone, first cousins are out there somewhere, mother was only child, and other cousins have not even acknowledged my request that they also test.

    • if i post my DNA with a 3rd cousin match from ancestry, onto Gedmatch, will we be able to tell if the link is maternal or paternal ? thanks

      • Sorry Wendy, there is no way to tell from those two tests alone. The companies cannot separate your maternal dNA from your paternal unless you have a parent tested.

        Additional cousin tests (and perhaps there are some at Gedmatch) would be needed.

        Sometimes I can tell which side a cousin is on by looking at the shared matches tab at ancestry

        • Great article!
          Challenge very similar to Wendy’s question, trying to determine if a 3-4th (adopted) cousin matches from her maternal or paternal line. We both took autosomal tests on Ancestry and uploaded to GEDmatch. There is a common match on Ancestry to a lady who shows as a 3-4th cousin for me (she is my half-2nd cousin, according to research) and a 1st-2nd cousin for the adoptee. I have done genealogy research and narrowed my search considerably based on possible ages from what she was told of her bio parents.

          I am pretty confident from the genealogy we all ultimately share a male ancestor, my great grandfather – I am from his second wife and I believe the adopted cousin, and our common cousin match are from his first wife – who happens to be his first cousin. Ack!


          • Has the adopted cousin given you management rights to their Ancestry DNA yet? After months of trying to figure out which of my gg-uncles was related to my own mystery cousin, I saw his line immediately in his DNA match list. He allowed me to post on the big sites and find chromosome matches. DNAPainter helped, too.

        • question: My sister and I share different dads, If my sister and i are both doing our DNA testing can we look at our matches and see who is different and assume that is on our fathers sides? or is the dna matching only for mothers sides?

        • So, this info is of no use to an adoptee who has no idea of her parents and who has no way to find the birth records because of sealed records laws is most states that DISCRIMINATE against adopted people. Is this worthless to adopted females, then?

  2. Through my ten years of testing, I’ve been told by genetic dna scientists that female half-siblings who share the same father would have 25 per cent on the X.

    Now, the question arises as to X testing with all these various salesgroups: Are they testing one X or both; and, if so, are they testing part of the X or all of both Xs in a female….

    • Will full sisters have the same identical DNA on the mother’s x chromosome? Mine is a little different than my sister’s..

      • Since woman have 2 X chromosomes, they will recombine them when passing their X to a child. Therefore 2 full sisters will have one identical X from their Dad and one with some shared chunks from their mother, very very rarely fully identical. Search for full sisters in the article above to see an example image from GEDmatch that has a solid blue line and 2 green bars.

  3. Donna either you are misremembering or were misinformed. The logic is clear. A man has only one X chromsome so he gives it unchanged to his daughters.

    The testing companies test both Xs, like the other 22 chromosomes, they have no way of separating them.

    • Mskitty,

      hoping you can help me understand how to use my X results from 23andMe. Trying to determine paternity. Have matched with a female predicted first cousin match at 1275 CMs across 39 segments and her nephew who had also tested. I match him at 809 CMs across 31 segments as predicted 1st cousin also. We all agree I am related to her as a her half sister or she is my half aunt (making him my half nephew or half 1c.) The “father” (her dad) has passed away, but his location and travels align with my mothers and she “remembers” him.

      another side note: This paternal family is middle eastern (where their culture does intermarry) so I wonder how that may distort DNA. He and the wife (mother of the half sis and gma of the half nephew) were 1st cousins (of other 1st or 2nd cousin parents).

      Our question is can we use the X chromosone to verify if she is my half sibling? Would it
      help to compare our raw data in GED Match?

      on the X – for her, I match genomic postion: 68411445-112741785, genetic distance: 31.89cM and number of SNPs: 3226 (23andMe predicted relationship – 1c, our guess – half sister)

      on the X for him, I match genomic position: 13867132-112741785, genetic distance: 90.59cM and number of SNPs: 8146 (23andMe predicted relationship – 1c, our guess – half nephew)

      If we are off base here, is there another way to prove if she and I are actually half sisters or if she is my half aunt or (even half cousin – if another male family member (like brother to this presumed dad) is possible.

      Some things to consider. This culture (middle eastern) intermarries. This family my presumed BF married his 1c on her maternal side. This presumed half sister is their youngest daughter. The presumed nephew is their grandson (his mother is their oldest daughter). I am wondering if I should try to test with the oldest daughter to be certain.

      • She is not your half sister since you do not have a full X match. Likely then your cousin.or aunt.
        Does she or her father have any brothers that can be tested? Or their children?

        • Hi,
          I am a newbie interpreting DNA and am collaborating with my brother in law who was adopted to see if he can find who is father was. All the potential fathers are now deceased but he has matched with two men in the same family – they are an uncle (A) and his nephew (B). The results are total 2071.1 cMs to B and total 1889.2 cMs to A. We are coming to the view that B is probably a half brother. Would that be right? I have looked at the Gedmatch graphics of the matches but can’t come to any conclusion looking at those.

        • Kitty I am sorry to ask but new to all of this… I am sorry to this lady that I am asking a question that nothing to do with her case but I urgently need to post a question . How do I do it?

  4. Thanks for the images! I still have a question regarding this:

    What if the half-sisters inherit the same X from their mother?
    F1 M1 M2 F2
    X1Y X2X3 X4X5 X6Y

    Same father: X1X2 and X1X3
    Same mother: X2X1 and X3X6 or X2X1 and X2X6

    Because the sisters can inherit the same X or 2 different Xs from their mother right? So if we see a high level of match, how can we tell if the sisters inherit the same X or if they have the same father?

    • Natalie the X a girl gets from her mother is a recombined mix of the two her mother has, so not as you stated

      For a child to get one X intact is very rare although I have heard of such cases, but certainly both sisters would not get that. For both non identical twin sisters to get the same X from their mother just does not happen although it is possible but extremely unlikely.

  5. I am trying to determine if I could be the child of one of two brothers. I match on an X chromosome with one of their daughters and share 26 % dna with her, would this be a potential half sister or could she still be a first cousin? In other words could brother’s pass the same X to their daughters? Could female paternal first cousins share the same X?

    • My sister and i tested 2,267 and we share the same mother.. we also believe that her father and mine are brothers. so that makes us sisters and cousins. I have tried to understand the solid green and blue line. its so hard for me to grasp. wonder if someone could check it out and tell me if we share the same father ? i don’t think we do. but i am a newbie and have no clue. thank you

      • Linda,
        The amount of shared autosomal DNA is consistent with your theory. To prove it look at the graphic at GEDmatch for the autosomal and the X. If the autosomal has lots of green bars (it does) which show where the two of you are fully identical (FIRs) then either you are full siblings or your fathers are brothers or closely related.
        Now the X will be a solid blue bar if you have the same father (it does not) and usually just a few segments (three in your case) when the fathers are related.

  6. kdiroberto –

    With 26% she certainly could be a half sister or an aunt or double first cousin; all of these are expected to be about 25% give or take.
    Yes brothers could pass the same X to their daughters since they only have one X to pass if they have identical X (unlikely more likely their X is 50% the same since it is recombined by their mother)

    So if you are female and have a full X chromosome match (the solid blue line) you have found your half sister. There is still the very tiny chance that both brothers got the same X from their mother but with the 26% autosomal we can say that this is your half sister, congrats!

    However if you are male you do not have any X from your father (or only a tiny amount at the tip of your Y) so then how much X do you share with her? That X comes from your mother’s side so suggests a relationship on your maternal line thus perhaps a double 1st cousin.

    • Thank you so much. I was hoping we were full siblings. However i felt we may not be .. I will look at the chart again. you are amazing !!! thank you

  7. Your child will be a perfect match on the half of the chromosomes inherited from you. So a solid blue lines on every chromosome and a 50% DNA match. Of course there could be a few tiny errors in the tests but the results would still be very close to that.

  8. My mother matches someone on the X-DNA for 50.4 cM on gedmatch but no autosomal DNA. Does this mean anything?

    • That is a good sized match. If you can compare at GEDmatch, lower the thresholds to say 5cM and 300 SNPs for the autosomal compare and see if anything shows up.

      If this were an a match on another chromosome, I would think 3rd or 4th cousin. However since the X can skip a generation in recombining this can be anything from a 4th to an 8th cousin I would guess. So contact this person and see if you can find a common ancestor. Let us know!

  9. My half-sister and our first cousin have all tested on 23andMe. We all match the full length of our X chromosome. Our father’s were brothers. Is this unusual that a cousin would match like this?

  10. Yes it is unusual but not as uncommon as you might think. Presuming you and your sister have the same father, your full match is expected since you both got one X as is from your Dad. In the case of your cousin, her father got the same X from his mother as your father did. Unusual but not impossible.

  11. I have found a full match on my 23 X chromosome to another male. He was born 1927 me 1957. The match is 15.5 cm’s 1155 SNP’s start location 108876094 and end location 119388467
    He is in America and me in the UK.
    The nearest names which match I have in my tree are like 200 + years back.
    I take it this match is from his mothers side of his family but wondered if the names link should be closer. I also have half matches on two other of his family both females. There are only half matches.
    Help I am confused.

    • Those 200+ years back names are just fine. X DNA can last a very long time, particularly if it goes from male to female to male to female …

      See my other article – – on X DNA for more explanations and links to other good blog articles like Roberta Estes’ X marks the spot.

      Even autosomal DNA matches can be that far back. I have a number of matches in the 1600 and 1700s. When you only match for one segment, due to the random recombination events there is no telling how long ago it may be from. Closer cousins, 3rd, 2nd, 1st, will usually share more than one good sized segment (8+ cM) that matches you.

  12. If your paternal half aunt has the same mother as your dad then you will share much of the X chromosome. Since your Dad’s mother passed along a recombined X to each of them it will probably be around half of the X. Remember, you got a copy of your Dad’s X unrecombined. Look at the full brothers diagram above for an idea of what the X from a shared mother looks like.

    • Thanks then we are not related at all..I tested via ancestry and she is not on my list at all..I transferred both test to gedmatch and get zero…I appreciate your answering.

  13. Would my paternal aunt’s daughter (aka my first cousin) share with me on the X chromosome? Would my paternal uncle’s daughter (aka my first cousin) share with me on the X chromosome?

    Is there any possibility that the first cousin would NOT share on the X chromosome?


  14. Both cousins are expected to share X with you but it is possible that they would not, extremely unlikely that both would not. Lower thesholds over at GEDmatch when you compare your X there. That is what I had to do for my double third cousin.

    Think of it this way, your father got a recombined X from his mother which He passed it on intact to you. His X is likely different from the one his sister, your paternal aunt, and his brother, your paternal uncle, got from their mother. Let us say they share 50% on the X with your Dad. Now your aunt’s daughter gets a recombined X from her mother so that would mean the expected amount you would share with her is 25%. However your paternal uncle’s daughter gets her father’s X intact so the expected share amount with you is 50%

    These can vary widely of course since recombination is random

  15. So, as a female if I get matches that share no shared X-dna, does that mean the info came from my father’s side?

    PS I have no other DNA from family members to compare against.

    Thanks for the help.

  16. My brother and I both tested at 23andme. Is there any way for me to determine which X segments are from my father and which from my mother?

  17. To some extent you can see which X segments are maternal since wherever you and your brother match on the X comes from your mother as his X is only from her.

    So anyone who matches both of you on the X is matching on your mother’s side. But the opposite is not necessarily true, someone who matches you but doesn’t match your brother on the X can be on a segment he didn’t get. You have to check the location carefully.

    However if your parents are from different ancestral populations, the chromosome view on the ancestry compostion page can show you which is which. Look at the image of my brother, me, and my father in my other X article for an example of that

  18. Going through my daughter’s matches on FT she matches two people on the X they are not related to me so I say they are on her dad’s side. They don’t match each other in the matrix utility they have over there so I would think one is on the mom’s side and the other the dad’s..I’m correct right?

  19. Now I run across this after I have had lengthy discussions in more than one forum about my cousins’ X compared to our aunt. I purposely had 2 female cousins who come from brothers of my father get tested to compare to my paternal aunt. And another male cousin whose mother was a sister was used, so it was very interesting to see. I have been getting help to map each segment of the chromosome. I knew what would be from my grandmother, but didn’t realize that it could be broken down further, my grandmother’s father’s or mother’s side could be distinguished. And of course whatever my grandfather contributed with his X but comparisons would only be present with my aunt and male cousin.

    Then there’s the unusual GREEN portionS I get on my X with my mother, but wondering if anyone else gets that with their X results?

  20. About a 2 months ago I found a half-uncle — the half brother of my biological mother — and we tested (autosomal). We share 12.9% dna, as expected, but nothing on the X chromosome. I was/am a bit concerned that we aren’t as close as the paper-trail suggests? Or could this just be a case of the X chromosome being “wonky” as it passes on — I didn’t get the segments he got?

    • CE –

      You said half siblings: if he shares the same father as your mother then they would share no X since his X is from his mother only.

      If they share the same mother, then he would share about 50% of his X with your Mom. So about 25% with you. But yes the X can be wonky. I would compare the X at GEDmatch and take the thresholds down. That is what I did with my double third cousin who just HAD to share some X with me since our great-grandmothers were sisters married to brothers.

  21. If a possible uncle and nephew had a test of STR Y chromosome test 16 loci and ten match is there a possibility they are related if the uncle is the brother of the nephews father?

  22. Tom – This sounds like it is not a paternal line match to me – 10/16? where did you test for only 16? An uncle and his nephew are expected to be a perfect match or possibly 1 off. I have heard of 2 off cases, but more than that is not that close a relationship.

      • By blood line do you mean DNA inheritance? If so then the inheritance is equal for a woman but not for a man. There are far fewer genes on the Y chromosome than the X, so a man gets slightly more from his mother who gives him an X than his father who gives hom a Y

  23. Kitty, thank you! This uncle is the half-brother of my birth mom, they share the same mother. Checked GEDmatch this morning, reducing the threshold as you suggested, and we do have 12 shared segments on the X, most of them between 1.0 and 2.7 cM, and 1 segment at 4.7cM, for a total of 23.4 cM.

  24. I have looked on gedmatch for the comparisons that you have in your article and have found something like what you have pictured. But there are no red lines and no blue lines. What do I click on to get to these comparisons?

    Thank You

    • These comparisons come from the one-to-one compare with Yes checked next to the question Show graphic bar for each Chromosome? on the form

  25. Hi Cousin Kitty! I have a full match share on the X with my mother, and full matches on two other chromos. Both parents Jewish, but different backgrounds — in my mother’s case, German documented back 300+ years. What’s the most likely explanation? Thank you!

  26. JoAnne –
    I am not sure I understand your question. How large is this X match? Are you saying that you have a match that matches the entire X for your mother? Else what are the cMs for this match to your mother? Which other chromosomes?

    Chromosomes can get passed intact, without recombining, usually the smaller ones and sometimes the X. See this picture of Brynne’s four generations of inheritance. Note that she has 2 chromosomes that came down intact from each of two great-grandparents:

  27. Using 23andMe’s Family Traits tool and GEDmatch X comparison gives me a rough picture of the amounts but not exact numbers. According to 23andMe FT, she and I share a total of 30 Mb fully identical, whereas everything else is a half-identical, as I would expect. Over half of the fully identical area is on the X. Comparing her to my sisters, she also is fully identical for about 30 Mb (same full match on the X). Is this common in endogamous populations? I haven’t seen it before! (I also wonder that FT uses Mb rather than cM, which 23andMe uses everywhere else, but i understand they are basically equivalent?) Thank you!

  28. No Mb are not equivalent to cM, very different, look them up in the ISOGG wiki –

    You can use FIA (family inheritance advanced) under My results > ancestry tools to get the cM at 23andme of the half match.

    The X match at GEDmatch definitely will give you numbers for the half match but not the fully matching section, as well as a picture of half and fully identical but as you say, no way currently to get numbers for the full match. I can ask the folk at gedmatch how hard it would be to get this data shown

    So if you have a full X match with your mother it means that she and your father are related. This is expected since you are ashkenazi. So the other half of your X is from your Dad and where you have a full match is where your mother and his mother were matching. X can last a very long time

  29. A recent email asked me why a woman and her brother got green lines showing a full match on both sides of the chromosome for their X compare when he has presumably just one X

    Research by John over at GEDmatch discovered that uploaded tests from ancestry and family tree DNA double up the single X in a male kit. Perhaps their databases require this for ease of programming

  30. My maternal aunt and I only share 15.3 cM on the x. Would this low of a match mean that she had different parents than my mother? She believed that she wasn’t the child of my grandfather. I’m wondering if she may actually be a 2nd cousin through a family adoption. If I lower the threshold to 1 I get a total of 125 cM. We share a total of 1061 cM autosomal DNA.

  31. Dee –
    DNA inheritance is pretty random. She could be either an Aunt or a half aunt – how many cM does she share at a threshold of 5cM – the numbers at ISOGG are based on that: 1700cM for a full aunt and 850cM for a half aunt. Can you get more family members to test? Your mother? Other siblings? Other aunts/uncles? 2nd cousins?

    The X is not conclusive either because she could just have gotten very different bits of X than your mother from their mother and you could have gotten more of your mother’s mother’s X. But it is extremely suspicious; both my brother and I share one segment of about 140cM with one maternal aunt and about 175cM with the other.

    So yes, a half aunt is quite likely. Do you have any 2nd cousins from the line of the parents of the grandfather who she suspects is not her father? Get them tested, if they share no DNA its proven or only 1 segment (which could be from a distant ancestor) then quite likely. You would need to analyze that segment further.

  32. Sadly I had a half sibling test performed by an English company who just used normal STR testing. The results came back as a slim chance of relatedness. If I had used x chromosome testing, I am sure that the results would have been quite different

  33. Hi
    I have a male first cousin (I am a female) and he matches me and also showing a large percentage of the X Chromosome. Do I match him via his Mother ?

    • Ms.kitty, I’m in much the same boat as Shirley. Ancestry connected me with a young man that was adopted and I ran our dna through gedmatch. Neither he nor I know our biological fathers so we are kind of lost on what the results are telling us. We match on 15 chromosomes. The largest segment is 162.8 cM. The total matches larger than 7cM=788.2 cM. I even checked to see how much we mached on our X which came out at 150.5 cM. Any thoughts would be greatly appreciated by us both.

  34. Hi, I have one X-Chromosome match (GEDmatch) which I do not share with my mother. How is this possible? Noise, Error or can these things happen sometimes. Being a man, means I can not have this X-match from my paternal line of course. But why do I not share it with my mother?? That´s odd. Can anyone help me out here? 😉

    • Where is the match on the X? How large? Try taking the defaults lower for your mother.

      If your match is to a woman it is likely a false match to bits from both her parents. The other possibility is an error in your mother’s results so lowering the threshold to 400 SNPS and 3cM will perhaps pick up the match for her

  35. Thanks mskitty, for the tip. It worked by lowering the threshold to 400 SNPS and 3cM.
    It Shows now:
    Largest segment = 4.6 cM
    Total of segments > 3 cM = 8.5 cM Actual.
    The same match (on my regular X-Chr list) shows: 7.3 7.3
    I think that happens sometimes. I´ve compared another match the other day. This match, luckily was listed on GEDmatch as well as on Family Finder. And on Family Finder this match was, as expected, lower (cM) than my mom´s. But on GEDmatch my cM results showed up higher than her cM´s.

  36. Hello… I am a relative newbie to all this, and quite frankly, find that even with the clearly spelled out in detail for me instructions, some of the DNA tools and what have you go a little above my head… That being said: I have a female match who is predicted to be anywhere from 2-4 cousin through FTDNA and 3-5 through Ancestry; GEDMATCH says our relationship degree is 3.8. She is adopted and I am thus far her closest match. We both only have autosomal results, although I am waiting for my delayed batch mtDNA Full Sequence results to come back in from FTDNA. What would be an easier way to determine where and through whom we are related? Help, please! 🙂 Thank you

    • ***Forget to mention: is it relevant, that we are NOT XMATCHES, and if so how can I use it to determine our relationship?***

  37. JBW75 – Great of you to help her out!
    Get as many relatives of yours to test as you can talk into it, 1st cousins, 2nd cousins, 3rd cousins, aunts, uncles, etc in order to have more data to work with. has a good methodology to follow as well.

    If you are male and you have no X match with her then perhaps you are related on your mother’s side, but X is peculiar and a non match is no guarantee except with very close relatives and even then …
    – Kitty

  38. Charam –
    You would expect to match about 25% of your aunt, your mother’s sister’s DNA. See the table at the ISOGG wiki:

    If you are asking about just the X, yes it is normal to share a fair amount of your X with your mother’s sister. I share almost the entire X with one of my mother’s sisters and about 80% of it with the other.

    Here is the comparison of my mother’s sisters on the X with me:
    Shared X with maternal aunts

  39. I had my brother tested using 23&Me. My test result is not back yet. I did a GEDMatch comparison on X and found a female that seems to match. Her mother was adopted. Then, I found a second match almost identical to the first two:

    Female #1: to my brother not adopted: Chr. 23 – 40,253,052 to 111,963 – 51..5 cM 2066 SNPs
    Female # 2 to my brother not adopted: Chr. 23 – 40,626,824 to 113,182,260 to 113,182,260 – 52.5 cM – 5619 SNPs
    Female #1 to Female #2: Chr. 23 – 40,626,824 to 113,182,260 – 52.5 cM, 5619 SNPs

    One other issue: My maternal grandfather’s father is “unknown.”
    I have tried reaching Female #2 without success, but I have shared info with Female #1 with nothing showing yet.

    Earlier relative comparison between my brother and Female #1 is not yet showing anything definitive.

    This “total newbie” is at a loss to know what this means. I’m an experienced genealogist, but DNA is totally new to me. Thank you so much.

  40. That is a good sized set of matches. Normally we tend to ignore matches that are just on the X because they can be quite back in time but these are large and they have triangulated with each other so are worth investigating.
    These people could easily be 4th cousins or 4th cousins 1R so look among your 3rd and 4th grandparents for a match. But remember X cannot pass male to male when looking at your pedigree.
    I share only X myself for 33cM with a known 4th cousin 1R. X that passes from man to woman to man to woman and so on can last longer in time than autosomal DNA
    Also note that these matches are across the centromere, an area not sampled by these tests as it has no SNPs of interest, which is from 58,632,012 to 61,632,012 on the X so these might actually be considered two segments. Not that that is relevant to your search.

  41. I am trying to determine if my father and his biological brother share the same father. Are they full or half siblings is the question. I have poured over forums and your website. I have uploaded their raw data to Gedmatch. I have done the one to one and x one to one. But I am still so lost. My brain is just not computing all the information. Any help would be greatly appreciated. I’m not sure if this information helps. But at the bottom of the one to one graph it says: Largest segment 174.1 cM Total Segments 7 cM = 2,860.9 cM and Estimated number of generations to MRCA = 1.2. The XDNA comparison is Largest Segment 59.0 cM and Total Segments 7 cM = 123.3 cM Actual.

    • Jodi, for siblings you only need to look at the Total Segments 7 cM = 2,860.9 cM – they are full siblings, same father, same mother. The chart at tells you that the expected number for siblings is 2550.00 and they are sharing more which can happen due to the random nature of DNA inheritance. The generation number of 1.2 tells you that as well; half siblings will be in the 1.5-2.0 range

      The X is not relevant for determining the father of a man since he only gets his X from his mother

  42. Wonderful! Thanks so much. I plan on reading up on all this more. I’m determined to figure it all out! I am horrible with math and science so this is going to be fun. LOL Thank You. 🙂

  43. Hello, I am an adoptee, female. I have two matches don’t understand. Match 1 on 23andme: a female. We share a single segment of over 90cM on the X only, no other autosomal. I have read that the X can travel several generations unchanged from father to daughter to father to daughter, etc. Does such a large X segment with no other shared segments point to this kind of transmission, or am I missing something? Match 2 on 23andme: a 1-2 cousin match with another female adoptee. We share 380 cM, but NO X at all. I think this might mean the common ancestor is a grandather (or uncle), with two sons, who each fathered a child with different women that ended up being adopted. Is that a correct interpretation of a possible scenario? Thank you!

    • PJK
      Have you been to DNAadoption? They have a great methodology for helping adoptees find their bio families.
      NO you cannot infer anything from the lack of an X match in people who are not close family. Is the 380 cM from familytree DNA? The best total to use is the total of segments larger than 7cM which GEDmatch will give you or you can figure out from ftDNA.
      Yes the large X match is probably around a 3rd/4th cousin, far enough that there could be no autosomal. Its size would suggest a close relative but that is not for sure … I myself have a 33cM match with a 3rd cousin 2R with whom I share no autosomal

  44. Husband’s DNA matches two half brothers with the same father, one with 165cM and the other at 137cM. When I checked for the X Chromosome match my husband only matched with the first brother and not the second. Can you explain this?

  45. Those half brothers have different X chromosomes since they have different mothers.
    It sounds like your husband is related to the mother of one since he shares X, but X can be from long ago. Since he shares autosomal with both, the likely main match is on the shared father’s line. Further investigation and triangulation would be needed to sort that out

  46. Kitty

    You have been enormously helpful. I am struggling with the X on the following:

    my mom (a foundling) found 2 1C through DNA. She shares 1006 cM with the male, and 905 with his female cousin. No X match with the male cousin. On 23andMe, she shows a match of 61 on X in two segments. On gedmatch, I discovered she has a match of 70.8 in two segments
    Chr Start End (cM) SNPs
    X 122,276 13,436,582 29.6 1,717
    X 22,673,384 46,997,457 41.2 3,032

    My mom is the daughter of either their aunt or their uncle (no known offspring of either, only one other daughter to test who is a sister to this female cousin). Does this X pattern suggest her parent is one of the brothers or the sister?

    Thanks for ANY insights, even if your advice is to accept that I will not know.

    • So is it the female cousin who matches X or is this some other match who has this X match?

      If it is the female cousin it really does not add information to the match. Remember females get DNA from both sides. So your mother has X from both her parents.

      If it is some other match, unless there is autosomal as well forget about it initially. Have you been to They specialize in helping adoptees

    • Then the male cousin would not share any X since he got none from his father who is your relative and that is the case.

      This means that you cannot use mitochodrial DNA to figure this out either, unless the maternal grandmother of these cousins has a female line descendant (or her mother or her mother). Then an mtDNA test of that person and your mother if a match would mean that the aunt is your mother’s mother.

      Many people confuse the X with mtDNA. mtDNA can solve a female to female line puzzle while X is more complicated since women get two.

  47. I live on DNAAdoption. They are awesome. It is the female cousin who shares the X. I was hoping since the shared X is two large chunks somewhat close to each other there might be a clue in there. No luck yet finding any sister to grandmama. And the one mtDNA match on 23andMe blocked us. sigh. No others have appeared.

    • I have thought about this some more and think maybe the X match does suggest which parent you have found.

      That amount of X is consistent with an aunt/nephew match 🙂 So it looks like the aunt is the mother of your mother but that is not a sure thing. Here is why:

      If the uncle were your mother’s father then the X match would look like a boy/other sibling match (shared mother) – usually about 90cM – 150cM in two or three segments from what I have seen. More than the 70cM in your match.

      That is because the X passed to your mother from a man would be a recombined X from his mother as would the X passed to the female cousin from her father. So the X match of your mother to the female cousin would look like a sibling match on the X if the uncle is her father. Most sibling matches I have seen are two much larger chunks. My brother and I share two 75cM pieces see the image in this article.

      I will go look at more sibling X matches in the next few days for you to see if I can confirm this.

      But remember X is pretty random and except in specific cases like whether or not two sisters share a Dad, it is not usually conclusive.

      Can you test that other person too?

      • Update:
        We have now found my mom’s mom. So the scenario in this discussion turns out to be: my mom was the daughter of a brother, and her X matches were with the two daughters of another brother.

        • Thank you for the update! I always appreciate more numbers and that makes perfect sense for that level of X

          Glad you found her family!

  48. Thankyou for the great info on here!

    I have had two sisters tested AutosomalDNA with different fathers, same mother.
    The father of Sister 1 is unknown & father of Sister 2 is known.
    The mother was adopted (known mother & unknown father… complicated!)
    There are three brothers and one more sister born to this mother plus another son who was adopted out (presumed to be of the unknown father) & not yet found.
    Brother 1 is deceased but there are 5 living children.
    Brother 2 the paternity is questionable.
    Brother 3 & Sister 3 are of the known father.
    All except Sister 3 have living children.

    1. where Sister’s 1 & 2 match can we safely say that dna is from the mother
    2. what would be your advice on who else to test to try to determine more about the unknown father?
    3. Does the X help rule anything in or out?

  49. To answer your questions:
    1. Yes as long as the match is about 7cM or more, smaller matches may or may not be real
    2. Test as many relatives as are willing to test. More data is always helpful. Test all the siblings since that way any large matches for sister 1 that do not match any of the other sibs would have to be paternal.
    3. Not yet but any large (more than about 20cM) X matches for sister 1 that are not a match to any of the others would probably be paternal

    Have you been to DNAadoption? Have you tested sister 1 at all three testing companies and uploaded to GEDmatch?

  50. Thank you

    Sisters 1 & 2 have a lot of big matches with Chr-4 being 171.2 & 36 cM with just a tiny red line in between and a full blue line ; Chr-15 is 101.7 cM with a full blue line.
    Q – does that indicate that this would be a complete Chr from the mother?

    They also have a 55.5 cM segment of the X – would that indicate that it is from the mother also?

    As yet we have only tested with ancestry and uploaded to Gedmatch and FTDNA. We were looking at doing the Full Sequence Mt on Sister 1 next and it has just gone on special for 20% off at FTDNA so hopefully we can get onto that one. Should we also do the Autosomal one with FTDNA & 23&Me?

    I have looked a little at the DNAadoption site but have to read through a bit more to find out what to do there.

    Your assistance is so very much appreciated : )

  51. Since the sisters have different fathers, all their matching DNA is from their mother. Yes it is not unusual for a chromosome to be passed intact although a bit more unusual for both sisters to get that unrecombined chr 15

    Full sequence mtDNA while interesting has no relevance to finding the unknown father as it is inherited from the mother. Testing more cousins/aunts/uncles can help sort out your matches better

  52. On 25 Aug, you asked if I could test that other person (sister to the female 1C, 1C to my mom). She tested! Results are in.

    Sister 2 X 2,812,568 13,408,199 22 1,775
    Sister 2 X 23,240,945 44,140,766 33 3,100
    Sister 2 X 53,161,383 67,881,743 4 600

    Sister 1 X 122,276 13,436,582 29.6 1,717
    Sister 1 X 22,673,384 46,997,457 41.2 3,032

    Whaddya think?

  53. Hi, thanks SO much for the post.

    In your opinion, if there are two females with known same mother and father and a third female sibling who is known to share the same mother but needs to confirm she shares the same father also, what test would you recommend? Would it matter much to include the mothers DNA profile also?

    • You three (or two of you) can test at any of the autosomal testing companies to discover if she is your half sibling or full sibling. However ancestry does not provide a browser to compare the actual data so you would have to upload to GEDmatch to determine that.

      Other than GEDmatch, only 23andme has a function that shows you the places where you are fully indentical (FIRs) which you will always have with a full sibling. Read my page comparing the test companies to make your decision but easiest for you would be 23andme:

  54. I have tests for myself and my 2 full sisters. There is a half match for all of us as expected. I march one sister on about half the X chromosome, and the other sister on about a quarter of it (not in the same area). Also the other two share roughly the quarter of the chromosome I don’t share with either of them.

    Given this situation, is there a way to “reproduce” our father’s complete X cr and/or a large portion of our mom’s? If it’s possible, is there a tool capable of this? And if so, could it be useful to have this very partial view of our deceased parents DNA?

  55. Yes it seems doable but how useful is the X? Better to get a lot of cousins on each side to do autosomal tests and try doing chromosome mapping that way I think.

    The term phasing is used to describe isolating which parent you got which bits of DNA from so use that to google search …

    To answer your X question, the ISOGG phasing entry mentions a number of autosomal tools, but nothing for just the X
    But if you are a whiz at excel you could probably do something with Tim Janzen’s excel script for your X
    I looked among the tools I have bookmarked and did not find anything
    Maybe pose this question on facebook or the DNA-NEWBIE list
    It seems doable

  56. Dear Kitty,
    I’m trying to help a friend discover who her parents were, both mother and father are unknown. My friend recently tested with Ancestry and 23andMe and uploaded to FTDNA and Gedmatch. On Ancestry and Gedmatch, among her best matches are 3 people from the same family (2 females and 1 male), with the common ancestor about 4 generations away. My friend has a 20cM X match with all 3 of these people. In addition, 2 other people from this same family have tested, but they have no X match with my friend and hardly any autosomal matches with her either.
    1. Does this situation indicate whether the 3 X matches are on my friend’s father’s or mother’s side ?
    Of these 3, each of them has a full 196.1 X match with the 2 others, while one female has a 196,1 X match with all 4 of the other family members who tested (with 3587.1 total cM in each case).
    2. What does this indicate with regard to the 5 person family ? Does it indicate who is on father’s or mother’s side within their family group ? What does it indicate about the family relationship of the female with the full cM ?
    I have not yet contacted any of them (actually all are managed by the female with the full cM).
    Many thanks for your help.

  57. The fact that there is an X match with the male in the group indicates that it is on his mother’s side. No help as to which side for your friend since she is female an gets an X from each parent.
    Have you looked at the methodology at ?

  58. Hi, Kitty! Sorry to dig up an old post, but I’m trying to see if GEDmatch could help me and an Ancestry-tested “first cousin” (who I’ve come to believe may be my maternal half-aunt) figure out whether she and my late mother had the same father. (I haven’t tried to have her upload her info. to GEDmatch yet, but I will if it will help us solve this mystery.) If they shared the same father, they would have shared one X. However, my mother has passed away and is not here to be tested, so we can only compare my data with the potential half-aunt’s. If I compare my own X chromosome data (I’m female, if that makes a difference) and my potential half-aunt’s, what should I expect to see if she and my mother shared a father? An approximate half-match on one X? Or is that not the way it works? (Many thanks for your patience with my ignorance. This has happened so suddenly that I’m trying to negotiate a very steep learning curve, both quickly and carefully, with two quasi-panicked families waiting eagerly for an answer!)

    • The likelyhood is that half your X will match her in either one or two pieces if she is your half aunt. BUT X sometimes gets passed intact so if your mother passed your her mother’s X there will be no match or her father’s X then a full match.

      So yes it is worth looking at over at GEDmatch but the answer may not be definitive via the X. The other autosomal matches will tend to be in. larger chunks for an aunt as opposed to a cousin so that may tell you.

  59. Dear Kitty: I am helping a friend find out who her father may be. Looking at just the X chromosome, Her half brother (they share a mother) matches his half sister at 141560176 to 155092994, with a 25.75 cm, 1767 snps. Another female we found matches the half sister only at 39227759 to 115389571, with a 60 cm, 2345 snps. What would the significance of this be? This Genetic based genealogy is very confusing for me…

  60. (I wouldn’t want my full name published, thanks.)
    Comparison between my sister’s and my x chromosome results at Gedmatch show a portion in which they do not match. Largest segment in common, 148.1 cM, SNPs 13,710. The left 1/4 of the comparison bar shows no match at all, i.e., no blue bar, and is a mixture of red and yellow bars. The right 3/4 of the x chromosome comparison bar does have that blue bar and is a mixture of thin yellow and green lines, no thick green lines at all. At FTDNA we show xDNA match on the visual chart of a non-match on the first half of the left bar but match on the right 3/4 of the bar. Viewing this in table, 26964786 154570039 147.74 14342
    . Gedmatch classifies us as 1.4 MRCA. FTDNA classifies us as either “full siblings, half siblings, grandparents, grandchild” [etc]. No reason at all to think we are anything other than full siblings, but I am puzzled at the lack of x match on the left 1/4 side of the chromosome? Can you interpret? Thanks in advance!

  61. Pat, I am sorry to say this but likely you are not full siblings, with different, perhaps related fathers. Full sisters will have a solid blue bar since they always share their father’s exact X.

    Else there is a massive error in one of your results. Did you test at the same company? Maybe retest one of or both of you. One other remote possibility is chimerism in your father. I recommend you consult with a professional if retesting shows the same result and you are sure you have the same dad

  62. Thank you for your answer. Yes, I did test with Ancestry and with FTDNA, and both had the same results. As a matter of fact, my mother had always said that she had at first dated the brother of the man she married, so this possibility will be something to check via autosomal matches at Gedmatch.

    It is understandably going to take awhile to process the information, but I very much appreciate your answering.
    Thanks again.
    Pat T.

  63. Hi, I’m trying to find matches to identify a 2nd great grandfather as follows … Me (female), my father, his mother, her father and then His father (or we could stop at her father). I am on 23andme, as is my aunt from same line (our grandmothers were sisters). Will I get any matches that will take me to my grandmother’s father or grandfather? thanx, jan

    • Try to get as many peohple descended from that 2nd g-grandfather as you can. That will help you narrow down matches from his line. If he is your brick wall then perhaps look at the techniques used at

      Also a Y test of a male descended on the male line from this ancestor could help find him as well

  64. I have a mystery here. I’m adopted and recently came up with a match on Ancestry and we took it to Gedmatch. I share about 2,047 centimorgans with this lady who is about 20 years my senior. We also share 151 centimorgans on the X chromosome in one large block (the ends don’t match). Gedmatch puts our relationship at 1.4. I have heard that it is possible to share the same father but have SNPs at the end that don’t match?? Is that wrong? She has an older brother who is testing soon but they can not work out how he can be the father. It’s a mystery to them all. They’re not saying it’s impossible just that it seems unlikely. Also, they really thought it was this lady’s father who was my birth father due to his having a second set of kids who are younger than me but no one can talk to him since he passed away years ago. Anyway, I also match with this lady’s daughter. We share 1,025 centimorgans on Gedmatch and share 95.8 cM’s on the X. Is there still a possibility that I’m a half sister to this match?? Or is the only scenario, given the X information, that her brother is my father??? Thanks so much, in advance, for any light you can shed on this situation.

    • Given that you are both female, you would have a full X match if you were half siblings with the same father. Thus judging from these numbers, she is your aunt, not your half sibling and her daughter is your first cousin.
      Hopefully the results from her older brother will clarify this

  65. Hi,

    My mom and her sister do not match completly on the X chromosome. I told my mom that I didn’t believe they had they same father (which has been family speculation for sometime). I just want to be sure.
    This is from GEDMatch:
    Chr Start Location End Location (cM) SNPs
    X 2,321 40,503,848 71.5 5,665

    Thank you!

    Image size reduction: 1/17

    Largest segment = 71.5 cM
    Total of segments > 7 cM = 71.5 cM Actual.

    • You are correct, they do not have the same father according to that X match.
      Another thing you can do is a one-to-one comparison at GEDmatch. Full siblings will have many green sections, those are areas where they match on BOTH chromosomes, paternal and maternal.

  66. Ok, I’m back with another question. So, my matche’s sister put her details on Gedmatch. She shares enough DNA with her sister for them to be full siblings and shares even more dna with me on the X than her sister does. She and I share about 165 centimorgans on the X and about 1639 centimorgans in total. Anyway, I mentioned before that my matches daughter (who is more than likely my first cousin) is on and we share 95 centimorgans and I share 151 with her mother on the X (my aunt). Anyway, why is it that my cousin’s mother’s sister (her mother’s full sibling) matches with my cousin on the X fully at 196.1 centimorgans whereas she and I only share 165 centimorgans. Is it that the mother’s X didn’t recombine when she passed it on to her daughter and that’s why the daughter and the mother’s sister are a perfect match. Confused.

  67. Have you compared your cousin’s mother and her sister on the X? They will have one identical X from their father and probably some identical X from their mother. So for your cousin to have a full match to her aunt she either got the entire paternal X from her mother or a matetnal piece from her mom that her aunt also has along with a paternal piece. In my experience the X from your mother is likely to have at most 2 recombination points and may have only 1:or even none. I have heard of a number of cases where X is passed unrecombined. As I recall, I have almost a full match to one maternal Aunt myself. Offline today, a travel day, so will check that later.
    Focusing on the X is a poor idea. Use autosomal matching first although X can help determine the nature of close family relationships as discussed in this article

  68. Recently a woman named M reached out to me on after she came up as a close relative/1st cousin (this is also how my maternal grandmother shoes on the Ancestry site). We both uploaded our raw data to gedmatch. This is what I have for M and myself:

    Total cM: 1788
    Largest cM: 137.3
    Gen: 1.5

    Total cM: 196.1
    Largest cM: 196.1

    M is 16 yrs older than I am and neither of us knows who our father is. I know this relation is on my paternal side because I match the X on my maternal grandmother and I also match an X on another woman named J but J and my maternal grandmother are not related. Both M, J and I shared several matches.

    For J and Myself, I have:

    996.2 Total cM
    91.5 Largest cM
    1.5 Gen

    60.4 Total cM
    34.1 largest cM

    For J and M, we have:


    936 Total cM
    77 largest cM
    2 Gen

    59.1 Total cM
    33.1 largest cM

    I used J because M and I suspect that one of J’s brothers is possibly our father. Is it possible, with these numbers for M to be anything other than a half sibling to me? I say this with the knowledge that we both know our mothers and they are not related.

    Thanks for any insight you can provide on this.

    I’m guessing that M and I are half sisters

  69. Miss Kitty,
    I found out that my mom had a child and gave it up for adoption when she was very young. After uploading my dna from ancestry and 23andme onto GedMatch, I got a hit on ancestry that I had a 1-2nd cousin who did not share any matches with anyone else on my DNA ancestry list. Not even my mothers brother. I had him upload his results to GedMatch as well and we have 482.6 cM total and the longest is 93.7 cM. We share no X at all, and he doesn’t match to anyone on my fathers side that I have found so far.
    Chr Start Location End Location Centimorgans (cM) SNPs
    2 122,315,053 196,838,012 64.7 14,826
    4 82,939,355 143,454,113 52.3 11,037
    8 4,749,173 8,243,226 7.9 1,222
    9 73,418,067 109,921,274 45.5 9,065
    10 88,087 7,123,444 19.7 2,791
    12 91,734,951 132,276,195 71.1 11,090
    13 27,313,217 30,883,921 8.5 1,143
    15 22,509,348 38,182,695 36.1 4,110
    16 27,926,696 64,735,494 29.3 5,285
    18 8,774,370 74,254,349 93.7 16,680
    19 10,735,616 51,478,246 42.1 7,081
    20 11,244 4,131,819 11.7 1,399
    Largest segment = 93.7 cM
    Total of segments > 7 cM = 482.6 cM
    Estimated number of generations to MRCA = 2.4

    I am thinking that he is my half nephew… Am I on the right track? It’s just confusing because he is not a match at all with my moms brother.
    Thanks for your help.

    • I took a quick look (no I do not do this for free so do not deluge me with kit numbers) and this is what I told Kate:

      Sorry Kate the adoptee you found is NOT related on your maternal side. I did one to one comparisons of you to him and your uncle to you

      There were several DNA segments where you match your uncle and the adoptee you found. These would clearly show as matches uncle to adoptee IF adoptee were related on your mothers side.

  70. I am 52, my DNA match is 35. I was told that my mom had a son who would have been born in 1952 +/- 1 or 2 years – so he would be 67 ish. No one remembers exactly and my mom has since passed and my two aunts tell different stories.

    I am trying to send you a copy of the actual bands but I can’t figure it out.

    Is this person more likely to be a cousin or related to my half brother.

    • The only way to figure out where this close relative fits in is by comparisons to other relatives.

      It seems most likely to be a match, thus a cousin, on your paternal side since there is no match with your mother’s brother. Presuming you match your mother’s brother appropriately so he is not a half brother…

      I will send you an email

  71. Hello Kitty,

    My husband compared his x DNA with a match. this is what showed up:

    Chr Start Location End Location Centimorgans (cM) SNPs
    X 2,321 38,017,572 66.6 5,001
    X 67,892,224 154,886,292 103.9 8,752
    Chr 23

    the top line is almost all green and the bottom is almost all blue. Does this mean he has a half brother or full brother from the same mother?

    • Thresta –
      A man has only one X chromosome so the green is not relevant. Nor can we tell if they have the same mother without looking at the autosomal match to see if they share enough DNA to be siblings. A half sibling will share about 1700 cM and a full around 2550 cm (plus or minus a few hundred) on chromosomes 1-22, see
      and the diagram below it
      That is a very very strong X match so likely a close relative.

      • Thank you for the clarification. Here is the autosomal comparison:

        Largest segment = 115.3 cM
        Total of segments > 7 cM = 2,156.6 cM
        Estimated number of generations to MRCA = 1.4

        I read you have to add the 170 cM from the x also.

        My husband was told his mother had an abortion but we are thinking she gave the baby up for adoption.

        Thanks again, Thresta

  72. Thresta –
    Use my contact form to send me the gedmatch numners and I will try to fit in a quick look before jamboree

    Also look at this chart at the DNA adoption web site
    That site also has a relationship calculator discussed here:

    • Thresta –
      I should have referred you to the article I did on telling a half sibling from a full sibling
      With no large green bars they are not full siblings
      The possible relationships are half-siblings or uncle (mother’s brother)-nephew or grandad (via his daughter) -grandson.
      I am working on a blog post about telling these relationships apart which is difficult.
      The size of the X match, the sizes of the biggest matching segments, the sharing one full chromosome (22) would indicate half siblings. More testing of paternal side and maternal side cousins is what is needed to resolve this.

      • Thank you so much! I really appreciate your taking the time to assist my family! We will keep digging and learning!


        • Hello again! I have made a bunch of progress. Just a quick question. Through my findings my husband and his half brothers (who share same mother) DNA match 2 brothers on someones tree but do not share any DNA with the sister. Does this mean the are related through the male side?


          • Thresta, no it is not meaningful. The randomness of DNA inheritance is such that each sibling inherits different DNA and the brothers happen to have inherited DNA that matches. Of course if it is a half sister then possibly you know something but you did not say how much DNA (at ancestry click on the little I n the match, there is a blog post here explaining that)

  73. Hi,

    We have been searching for my husbands father. We sent his dna in to ancestry a couple of years ago and we recently located someone who we think may be his half brother. The person we think is the half brother has sent his dna in to ancestry. We are waiting for that to come back. We have also put my husbands dna on to gedmatch. When we upload the other person to gedmatch what should we look for. Will there be a solid blue line on the x chromosome if they are a match. I am getting very confused on what to look for.

  74. Hi there! I am wondering about a strange result from GEDmatch (at least, it seems strange to this newbie!) I have a match with whom I share 60cM (one solid segment of that length) on the X chromosome, but when I compared our autosomal DNA, there was no match. I had to lower the threshold to 300 SNP and 4cM to get anything, and then our one matching segment was just 4.8cM. How can we share such a huge chunk of X and almost no autosomal? What might this mean for our level of relationship? Thanks so much for any insight you can offer!

  75. Jessica –
    Perfectly normal to only match on the X. I share a 33cM segment and no autosomal with a 4th1R. Yours could be that or a 3rd 1R or ???

    See my other article – – on X DNA for more about that.

    When you only match for one segment, due to the random recombination it can be far back, although not usually that far for a piece this big. Closer cousins, 3rd, 2nd, 1st, will usually share more than one good sized segment that matches you whether X or autosomal

  76. Hi Kitty, question that should be simple but I don’t see anywhere in blogs: what’s a “strong” match for X-chromosome? To answer this, I need to know max # of cM (or SNPs) on the X… is it the same size as the rest of our chromosomes?

    Do you know of a source for the cousin matrix for X that others have shared for the autosomal results? That’s so helpful to keep in mind the RANGE as well as the median! Thank you!

  77. Susan –
    Here are some rough numbers for “good” X matches, more than 10cM female to female, 7cM female to male, 3cM male to male.

    There are about 182cM on the X at 23andme, 196cM at GEDmatch see (it depends where tested)

    Because of the differences between men and women and the way X can last a long time when it is passed male female male female, it is just not possible to do an accurate cousin matrix for the X. Would you do a matrix for just chromosome 1? A single autosome is not useful statistically for matching, it is the whole group that makes the difference. X is excluded from the group used or atches at most companies because of its different inheritance patterns which can lead to large matches with distant relatives and none with closer ones.

    For example, my Dada and I share 33cM on the X with a 4th cousin once removed from an ancestress who was born in 1729 and no X with many a 4th cousin with whom we could share X with. We share a 25cM segment on the X from the 1600s with another group of cousins.

    We tend to use the X to help with narrowing down which line unknown closer relationships are from. It is not very useful for predicting the degree of cousinship due to its inheritance nature.

    See if this other post of mine helps –

  78. Hi Kitty!
    Im and adoptee and was hoping you could help me figure out if this person is my uncle or not. On gedmatch on a one to one compare the results came back as:
    Largest segment = 157.7 cM
    Total of segments > 7 cM = 1,490.4 cM
    41 matching segments
    Estimated number of generations to MRCA = 1.6
    It also shows that we match on the X with 12.8cm.

    Im not sure if this is significant or not but the mother of this person has an identical twin sister. Is it possible that this person may be a double first cousin rather than an Uncle?

  79. Ashley, there are lots of possibilities… uncle, half sibling, cousin where he is the son of your mother’s half sister, double first cousin (two brothers marrying two sisters) or grandparent. The X makes it likely he is related to you on his mother’s side but is not conclusive. It is low for an uncle. It could easily be from a far back ancestor rather than a recent one.

    I will email you and look at the two kits on GEDmatch but the only certain way to tell these relationships apart is to test more of his family members. If a close cousin on his Dad’s side does not match you then he is not your uncle.

  80. Can you please tell me if I would get a more accurate result testing my half brother (on my fathers side) or my fathers brother, my uncle for Paternal Lineage?

    • Your father’s brother is one generation back so his autosomal results would be more interesting to you. Either one of them is fine for a Y chromosome test, although your known half brother is a surer thing (in other words what if your uncle had a different dad than your father? unlikley but it does happen)

  81. mskitty, My mother and I recently got our results back from 23andme and I am having a hard time making sense out of the relationship to 2 predicted first cousins (a brother and sister). They both are listed as first cousins to my mom, and second cousins to me. My mother was adopted and only knows that she was born in San Francisco in 1943. Both of the predicted cousins and their immediate family are from that area.

    I am a 9.30% match to the sister sharing 23 segments (no match on the X) (half IBD 693cm) and match 8.53% to her brother sharing 25 segments (no match on the X) (half IBD635cm).

    My mother is a 15.9% to the sister sharing 33 segments (3 segments are of the X) (half IBD 1181cm) and match 15.1% to her brother sharing 32 segments. (no match on the X (half IBD 1126 cm)

    Could you give me some insight as to what the relation is for my mother to each of them and what side of their tree should I focus on to learn about my mothers birth parents? Any other tips or help that you could offer would be a blessing.

    • Marcus –
      It is hard to tell the exact relationship from these numbers. They are just a little too low to be half siblings to your mother. The likely relationships are half niece and nephew (children of your mother’s half sibling, probably half brother since boy has no X) or first cousins – children of your mother’s aunt or uncle (the sibling of one of her parents), likely uncle since no X with the boy.
      There are many helpful resources at DNA adoption. They recommend going slow with birth family contact, see
      A problem with 23andme is that the testers there are often looking into medical and have not set up their profiles to get an email when they get a message via the messaging system. So you many not hear back right away.

  82. Thanks….My mind is about to explode trying to make sense out of all of the possible connections. My mom and I did reach out to my predicted first cousin and she has been great with sharing as much information that she believes to be true. She also provided me with as much of her family tree that she knows of and it seems to be pretty well documented with the exception of how my mother came to be. My predicted first cousin is also very curious to know what our true relationship is but is also a newbie to this as well.Would it be ok if I sent you a few things via email to look at? I don’t expect you to spend much time on it but if you could just take a look and let me know which of the people on the tree I should put extra emphasis on, again would be a blessing. This part of her tree is complicated to me and I’m simply overwhelmed.

    FYI – All of her elder’s are deceased.



  83. A predicted first cousin is often actually a half sibling. Is your mother adopted? There is much information at the site and if you are on Facebook, there is a group DNA detectives there that can help.
    I will email you as well

  84. Hi Kitty, Would you please advise? I have read and reread your blogs (thank you for the articles and direction). With the numbers that are showing I am showing a half sibling connection along with the same biological father. I can send you the Gedmatch numbers if you would like. Here is how it is looking:

    Ancestry DNA: 1,675 centimorgans shared across 53 DNA segments.

    Gedmatch: Largest segment = 131.2 cM / Total of segments > 7 cM = 1,736.0 cM / 37 matching segments / Estimated number of generations to MRCA = 1.5.

    There is blue in every Chromosome on Gedmatch as well as the X which is a blue solid line all the way across. X info: Largest segment = 196.1 cM
    Total of segments > 7 cM = 196.1 cM Actual.

    I read further up in your article that a solid blue line on the X means the same father. I am not savvy with this and would really appreciate your input.

    Here is the chart from Gedmatch on One to One Autosomal:

    Chr Start Location End Location Centimorgans (cM) SNPs
    1 742,584 20,023,585 44.8 3,605
    1 48,924,473 201,397,294 131.2 16,810
    2 42,997,091 129,482,940 73.3 10,223
    2 217,161,866 242,656,041 46.5 4,300
    3 36,495 11,140,909 29.3 2,811
    3 114,852,700 153,012,811 41.6 5,162
    3 153,037,439 171,441,246 10.5 1,709
    4 3,679,273 36,624,746 50.1 5,079
    4 141,030,150 187,838,956 64.1 6,465
    5 9,670,945 38,349,568 36.6 3,913
    5 122,437,333 132,705,069 8.6 1,285
    6 11,942,463 138,951,354 117.3 16,748
    7 140,018 43,771,220 64.1 8,048
    7 144,802,847 158,737,504 32.0 2,454
    8 11,876,341 38,693,523 37.3 4,756
    8 137,069,094 146,241,933 16.8 1,577
    9 11,870,490 104,186,704 79.9 10,018
    9 111,707,724 140,128,836 50.4 4,908
    10 103,934 7,055,200 19.6 1,814
    11 192,856 9,635,721 20.5 1,957
    11 121,568,793 134,396,557 28.7 2,800
    12 61,880 3,586,646 9.4 768
    12 45,639,854 121,198,889 80.8 10,453
    13 35,045,665 109,169,265 84.7 10,823
    14 18,397,823 29,132,953 22.6 1,955
    14 30,063,546 106,215,123 100.9 11,201
    15 18,331,687 30,757,435 24.1 1,596
    16 41,263 5,906,038 13.9 998
    16 83,679,234 88,668,856 12.0 1,236
    17 67,740,439 76,433,198 27.8 1,917
    18 102,535 10,376,324 37.8 2,580
    18 14,725,684 68,829,022 62.0 7,711
    19 211,912 2,964,374 8.2 553
    19 51,968,294 61,383,413 33.0 1,936
    20 11,799 62,364,868 114.7 11,060
    21 13,591,802 38,689,744 47.8 4,270
    22 15,437,138 41,963,405 53.4 4,294

    Thank you!

  85. I match with a female on Ancestry as Close family; 1750 cms across 46 DNA segments; Gedmatch shows her as 1801 cms, no X-DNA

    By eliminating my maternal DNA matches, she matches somewhere on my paternal side, but where? She and I, as well as her siblings and mine are all within similar age ranges.

    This female is a fraternal twin.

    On Gedmatch this female shows as a 1.5 match with my sister’s son, he is a known nephew; 23andme shows them as 1st cousins; they share 957.8 cms. NO X-DNA between them. I share 130.1 X-DNA with my sister’s son, which is to be expected because we share the same mother.

    X-DNA is confusing the issue. What happens to X-DNA with fraternal twins? Is that throwing off the X-DNA?

    If she is my half-sister on my paternal side, would she share X-DNA from my sister’s son?

    What would you anticipate the relationship? I have researched this inside out.

    Some have said that since she and my nephew share no X-DNA she is not a half-sibling, but one of the other relationships. I can’t see how this could be, but maybe it is.

    To confuse it more, we believe my father may have been adopted so we haven’t yet been able to develop a paternal tree, but have a lot of Ancestry DNA shared matches, and 103 shared matches with this female. Of those 103, I have been able to see two distinct lines, but as yet have not been able to identify the maternal from the paternal (along my father’s line).

    If it were not for the X-DNA I would say she is my half-sibling, particularly because of the age scenarios.

    Your thoughts would be appreciated!

    • She is most likely your half sister sharing a Dad.

      No X is totally expected because you got a Y not an X from your Dad so expect to share no X with any half siblings who share your Dad.

      The other possibility is an aunt. To remove that possibility you could test a first cousin from her maternal side. If she is your aunt, you will match her maternal cousin, if she is your half sister, you will not. If she were your niece, she would match cousins on your maternal side

  86. So I’m very novice at this dna, but I’m attempting to help an elderly friend “peanut” find out who his biological dad was/is. I’ve uploaded his ancestry dna results to gedmatch ( A215747 ) Is it safe to through out any and all x matches (knowing that they would be a maternal match) ? Or is there something that I’m missing and a possible way for an x match to be paternal? Thanks,

    • Far better to get some of his maternal relatives to test so you can eliminate their matches

      Yes you can eliminate folk with large X matches BUT … If his parents are from the same population group, he could share a small X match with a paternal side cousin, an autosomal match, where the X is actually, of course, from”peanut’s” maternal side because X can go so much further back in time.

      Have a look at the methodology at and watch for my next blog post

  87. I am trying to find out how an unknown cousin is related to me & saw that we share X-DNA. I was looking on-line to find out about the rules as to how X-DNA gets passed down, etc., I just happened to notice that a known cousin & I share X-DNA & we shouldn’t. My paternal grandfather (who I shouldn’t have received any X from) is the brother of her great grandmother.

    This grandfather (paternal) happens to be German, maybe with a little English, but the rest of my grandparents are all Portuguese. Both of my grandmothers are from the Azores; Sao Jorge & Pico. There are not that many more on the German side of the family who came to this area (we started in Sausalito, they started in San Jose) but there are a lot of Portuguese in the South Bay. I have contacted this cousin that I have the X-match with to see if we can figure out if we might be double cousins!

    When I was looking through my X matches on GEDmatch, I also noticed that I have an X match with a kit that you administer, her name is Azore Rose. I don’t know if you have the liberty to share any information & I know that you are busy with your own paying clients, but if there if there is anything that you could let me know off-line, I would appreciate it. It’s a small match (6.9) & she does not match my mother, so it is probably from my paternal grandmother, who’s family if from Sao Mateus, Pico. I can share their CITEM pages if that helps.

    My GEDmatch number is A953616

    Thanks for your informative site!

  88. Unless the X match is large (>10cM), it is often not worth following.

    You can easily share X with someone not on the X pathway just by being in the same population group because it comes from long ago on another line.

    For example I share 11cM on the X with my AJ husband who is not related in the last 500 years … but I have a jewish maternal grandad, so somewhere way back … I also share 7cM with genealogist Judy Russell who is also not related within a findable genealogical time frame, but like me has German ancestors (maternal grandmother for me).

    (and yes I forwarded your message to Azore Rose who has Azores ancestry but she is not online all that often)

  89. Dear Ms. Kitty,
    My 23 and Me resulted in an 18.1% match with a prediction of half sister but there is nothing identical on the X. What could this mean?

  90. This amount of shared DNA is on the low side for a half sibling. Is this an endogamous group? Could it be a first cousin where both parents are related to yours? That would explain the lack of X

    To share no X with a female to female half sister is extremely rare but not impossible. You would have to have the same mother who gave you each a different X.
    However it might also be aunt or a grandparent. See

    To share no X would be more likely there but still unusual when you are both female

    • Dear Ms. Cooper. I hope you can help me as well. I was a long time member of the DNAadoption site and helped many others but can’t seem to help myself.

      I found my birth mother over 30 years ago. I found out after DNA testing that who she said was my father was totally ruled out. I came back 51 per cent Ashkenazi Jewish with over 5000 matches at this point. I had a real breakthrough in that I finally got a match at 487 cm.
      The match is female. I don’t know for sure if she is a second cousin or a 1/2 first cousin since her mother had 3 half brothers who had a different mother. Her mother was the product of the grandfather’s second marriage.

      I just realized that we do not share X. Does that totally mean that we are related through the half brother of her mother? Names though seem to correspond more to her father’s side of the family, yet I don’t share enough DNA to be a full cousin. Is it likely because of sharing no X that her half uncle was my father?

      Thank you so much.

  91. No X is not always significant but for close family like this makes it likely that your relationship goes through two men.

    Jewish match numbers are close to.the norm out to 2nd cousins so your scenario, half first cousins is possible but also look at other descendants of the granddads parents for 2nd cousins …And also check 1C1R

  92. So, what would a mother and daughter’s X chromosomes look like? All blue on the bottom, and mostly yellow with some green and some red on the top?

  93. Yes, not much red though (those would be errors in the kit since they should always match on at least one side. I will post an image here too.

  94. Dear Kitty,
    My brother, sister, me and one maternal uncle have tested w 23andme. I compared the x-chromosome overlaps from each of us with our uncle. My sister and he shared about 61 cM, and my brother about 74 cM on the x chromosome – I shared zero, despite sharing a total of about 28% of my DNA with him, including every chromosome except X, and also sharing 184 cM with my sister and 96 cM with my brother on the x-chromosome. Does this mean anything?

  95. Hello. I found a match with what appears to be a half-brother (or uncle) on 23andMe. I am a male adoptee, and the match with whom I share 26.7% of my DNA is also a male adoptee. My question is this, if the two of us have 39.04 cM (3,559 SNPs) on the X chromosome listed as half-identical, and another 40.00 cM (3.653 SNPs) on the X chromosome listed as completely identical, is it likely that we share the same mother? My understanding is that none of X chromosome would have come from our father(s), but I am still unclear about the significance of shared segments on the X chromosome.

    • Yes you are related on your and his mother’s side. Either you share the same mother or he is your mother’s brother (or vice versa).
      You can ignore the completely identical designation. It is all half identical since a man only has one X.
      Feel free to send me the kit numbers via my contact form and I will have a look. What are your relative ages? (send that and where you were each adopted from/born)

  96. Dear Kitty,

    I am so glad I found your site! This post has been extremely helpful!!! However, I am new to this subject, and still have a question. I have not read every single reply in this thread, so please forgive me if I ask a question you have already answered. I tested with 23andMe, Ancestry, and Family Tree DNA. I have a match (I am female, and so is she) on Ancestry and 23andMe that says we share 2,243 centimorgans and have a high confidence score that we are immediate relatives (we are both adopted). I have come to find out our mothers are sisters. She knows her birth father also; I do not. I have been told that our shared cM count is pretty high, higher maybe than just cousins–that perhaps we also have the same father (or maybe his brother is my father). I just uploaded my results to GEDMatch, so I am waiting to see what I can learn there. I am guessing we could just compare our X chromosomes to figure it out???

  97. Male adoptee here who found a 2nd cousin DNA match who is helping me with his family tree. I’m hoping to isolate if I’m related via my mother or father. I don’t have an X match to them but we both share some distant autosomal matches that I also happen to match on X (i.e. autosomal matching 20-30cM and X match is 10-12 cM). Is it likely then I am related to this person via my mother or is still inconclusive? thanks!

    • Its likely but by no means conclusive.

      X can last a long time and if your parents are from the same population group, the X can easily be way back on her side while the autosomal is on your dad’s side

  98. Hi Kitty! So my big question is… My sons ‘potential fathers’ DO NOT share a father. The brother that I KNOW is the father (sex was MONTHS apart), after a 99.97% DNA match, claims there needs to be special testing to determine paternity. Being half brothers, not sharing the same biological makeup, does it require a special test to determine which brother is actually the father? Im tired of fighting about this… Please help!

    • What tests have you done? Not clear from your question. Sometimes people just need time to adjust to this. Give him some.

      There really is not any doubt with ancestryDNA or the like but those tests are not acceptable in court whereas regular paternity tests are.

  99. Hi Kitty I hope you can help me with a question. I have been working on my mom’s DNA and it is very confusing. I have ran across a Paternal match of a half brother and half sister that is on Ancestry and on Gedmatch. According to Ancestry they are my mom’s 2nd cousins, but according to our family tree they should be 3rd cousins (their great grandmothers were sisters). The female and my mom share 313 centimorgans. I noticed on Gedmatch that they also share 58.8 centimorgans of X DNA, and 5,335 SNP’s. The top line is Red, Yellow, and Green, and the bottom is a large gray line, a long blue line, and then gray again. Above the long Blue line is large mix of yellow with lines of green. It looks a lot like the very first graphic you shared, except there is only one blue line. It also says they are 2.8 generations apart. Can you help me make sense of this? I don’t know where this person falls in our tree, or the relation. Thank you so much for your help, and your site, it has been most helpful!

    • Adrian –
      That amount of shared DNA is expected to be a 2nd cousin. What is the age difference between those great-grandmothers (could one really be the mother of the other and the family raised them as sisters). Are there any additional shared ancestors? Are the parents of those two great grandmothers closely related, for example first cousins? Or are they from an intermarried population group (endogamous) like Arcadian, Mennonite, Jewish, Polynesian, etc. Lots of possibilities …

      • I went and looked and the sisters are only 6 years apart. Their parents are not closely related, and they even come from different counties as far as I can tell. As far as I know they were not intermarried, and not from any of those groups. There are no other shared ancestors that I know of. That is why I am so confused. My mom’s paternal line is just not matching up to what I have on paper, and this new connection has really thrown me for a loop. I have messaged both of the half siblings, but neither will respond to my messages. Thank you for your response!

        • After a little further research I found they had an error in their tree. They had their great grandmother listed as their grandmother. The missing person is a half sister of my mom’s grandfather. Thank you for your help!

          • Delighted you resolved this Adrian. Often we genetic genealogists have to use our genealogy skills to fix the trees of our new relatives!

  100. Hello…hope you don’t mind me reaching out… I am trying to interpret some gedcom results.

    I am trying to confirm if I have a half niece or a first cousin. Her father was adopted and I believe either my grandmother or mother might be her father.

    We tested our X on gedmatch. The total CM is 100.6 with the largest segment being 83CM.

    Is there any way to use the X Chromosome to help confirm the relationship?

    • JPC –
      Not really. The X is just one piece of evidence. If you are male then only your mother’s side will have given you any X.
      The amount of matching autosomal DNA is far more important in determining close relationships but a half niece and a first cousin share the same approximately 12.5% or about 860cM. The half niece may share more larger segments.
      Try getting some close cousins on your mother’s father’s side to test. They will match if your mother had her father and not if your grandmother had him.

      • Wow – thanks for the reply. I did find some people who match the criteria you mention.

        Would it matter if my grandmother had a child with her husbands brother? In this case she was a widow and her daughter (my mom) were both in child bearing years.

        If my daughter is tested, will that shed any light on resolving the paternity question?

        • Yes it would matter and very much confuse the issue if your grandmother had a child with her husband’s brother. The shared autosomal DNA with you would be roughly 1/4 more than expected than if it was a non-relative she had the child with.

          Your daughter’s test would not be particularly helpful for resolving this case as half her DNA came from you. Your siblings may be useful, but second cousins will be best.

          This article may also be helpful

  101. Hi Kitty.. time for a dumb question – relating to hereditary of X-DNA. I found a third cousin match through FT-DNA a while back, 212 cM total shared. The lineages from myself and her to our common ancestors were: Me ->Dad -> Granddad -> G Grandmother -> common ancestors; and for my 3rd cousin it was Her -> her mum -> her grand-dad -> her G granddad -> common ancestors. All fine with that; but when my sister did DNA test (and she is my full sibling from DNA analysis) – she came up as an equally strong match with this 3rd cousin – but also as an X-match (3 segments of 3+ cM; respectively they were 4.9, 3.3 and 17.6 cM). My understanding is that if there are two males in succession in a lineage (e.g. in this example BOTH from my father to Grand-dad; and in 3rd cousin’s case, her grand-dad to great-grand dad) – then you don’t get passing on of the X-DNA, correct ? Is there any possibility of false X-matches in this type of scenario?

  102. Thank Kitty – that certainly helps. Just to be clear – might you be suggesting that while the degree of total autosomal match of about 200 cM is consistent with third cousins (which is what our trees support) – that the X-DNA segment of 17.6 cM that my sister and 3rd cousin share is probably coming from further back than that ? Probably another line? And the fact that my sister has the X-match but I don’t – does that mean necessarily that her match is coming from our paternal grandmother line – or could it be just as likely from our maternal line ?

    • Mal, yes further back and another line, exactly.. and it says nothing about your match. Unless there is geographic proximity that suggests the paternal grandmother line, there is no particular reason to think the X is from there. In other words, that X could be from the same population group as the autosomal but there are no guarantees …

  103. I’m confused about matching with someone on the x chromosome. If you don’t know how you are related to a match, will matching on the x chromosome help you figure that out?

  104. Hi Kitty,
    May I submit the following for your comments ? I have built a mirror tree with 7200 people in it, but lack direction at the moment…
    1. Francine, for whom I manage the mirror tree, has a 19.8cM X match with RO, who is a man (Francine being a woman, if this was not obvious !). I have traced how this X match might be transmitted, according to the usual method of transmission. When I attach Francine’s DNA on Ancestry to the people who might be carrying the X, the result is that Francine has an autosomal match with someone called Leslie that follows the exact same path of transmission of the X, through 7 generations. In fact, the autosomal match string concerns ONLY the person who might have the X, not that person’s spouse (except at the 7th generation, where the autosomal match concerns both husband and wife). RO and Leslie are NOT ICW, according to Gedmatch, nor are they ‘shared matches’ on Ancestry.
    Is it likely that the autosomal match string with Leslie is Francine’s mother’s line of ancestry ?
    2. Gedmatch finds that Francine’s mother and father are related, with a 7cM match on ch 7. Francine has ICW autosomal ‘one-to-one’ matches with two people (neither RO nor Leslie) on ch 7, at 13.1 cM and 8.2 cM respectively. However, although their segments overlap completely on ch7, these 2 people are NOT ICW each other.
    Could one be on the father’s side, the other on the mother’s ?
    Many thanks for your help.

    • James-
      Is Francine an adoptee you are helping or ? I am not following the first question. Stick to autosomal first. Leslie may be related on a different line, unless you can see the exact segments at GEDmatch, you do not know much.
      As to question 2, try dropping the defaults lower when you compare the two matches. Since Francine has identical DNA from each parent for that segment, anyone she matches there should also match each other unless one is a false match (the 8.2 most likely). Are they tested at different companies so that some of the inferred DNA could be wrong?

  105. I have found someone that may be a half aunt but I cannot decide if she is paternal or maternal. the x chromosome on gedmatch shows basically the similar match as the half sisters on the top of this page but I believe she is paternally related. we are both female. the cm is 1071. here is my chart please help me.. im adopted and so is she so I know nothing.
    Chr Start Location End Location Centimorgans (cM) SNPs
    X 39,513,581 154,886,292 126.6 11,853

    • That large an X is more likely on your paternal side but no guarantees. I am in the middle of a new post trying to explain the technique for adoption DNA searches with ancestry and GWorks from DNAgedcom. Have you looked at the methodology at

  106. My 85 year old Mom ( living) was adopted at age 7 from the NY Foundling . Birth parent info is unknown. My mom and I match a person on the X Chromosome -A female –Mom=22 total cM largest 11.4 and me 11.2 total with 11.2 being the largest. We also both match Autosomal mom=30.7 12 segments and me 12.5. Would this signify a valid relationship somewhere across the generations?

    • Kathleen –
      This sounds like family tree DNA numbers, what are the totals of segments > 7cM ?? This is likely a relative but could be quite distant

      I really recommend you test your mom at ancestry, it has such a large database that you may have better luck finding closer family. Also with the method described in my most recent blog past you can figure out her family from 3rd and 4th cousin matches

  107. Thanks Kitty. We did test on Ancestry and they have a match to Mom for a possible 2nd cousin-269 cM with 15 segments. ( I match as well as 3rd cousin) Person is a female with a family tree with some information ( not great detail) . Person appears to be in her 30’s based on internet searches and her mom about 65 yrs old.
    Would the match mean a relationship? The person did not upload into gedmatch. Both Mom and her 2nd cousin match also match a third individual as 2nd cousin ( no tree at all) moms match was 2019 cM across 14 segments . Where would I start to unravel this relationship and would it be GG parent or GGG based on the age differences

  108. I am currently trying to research my brother in laws ancestry. He was adopted and illigitimate and knows nothing of his father and very little of his mother. Having taken an DNA test it has flagged a 1st/2nd cousin link with a lady who coincidently was also illigitimate, their autosomal comparison is 18 matching segments in 13 chromosomes with a total of 641cm and the largest being 84cm the x chromosome match 64cm.
    I understand the basics of x chromosome transference but cannot make an educated deduction.

    From this data is ther anyway of knowing if they are related on my brother in laws maternal or paternal side, or the lady in question?

    • Margaret there is no way to know which side since a woman gets an X from each parent. Comparisons to other relatives can determine this. If they share the entire X, about 196 cM, then they usually share a father

  109. I was adopted at birth I did 23andme as well as I Ancestry DNA I already had located my maternal side. I was looking for my Paternal side. Ancestry was the biggest help. I had several 2nd cousins. Anyhow, once I figured out whom my father was, I also had 2 sisters. They too did there DNA. here is what is interesting. On my maternal side: I do not look like any siblings as well as personality traits. I have matches on chrom 23 “X” with them but not a ton. On Paternal side, I have as Kitty said, full “X” ( All three of us sisters ). I look exactly like my father and they kinda do. I have one sister on Paternal side that matches my CM as 2180 the other 1560 cm. The one sister that I match at 2180 ” You would think we were whole sisters we are so alike.” We also match on 2 different chr totally. I am trying to figure out if “Kitty” has a blog about what each Chr means 1-22 explaining the matches on these chr’s in detail? Can anyone help me or tell me where to find an article?

  110. Mskitty (i posted in an other thread earlier…..figured I needed to start a new psot, not a reply post).

    hoping you can help me understand how to use my X results from 23andMe. Trying to determine paternity. Have matched with a female predicted first cousin match at 1275 CMs across 39 segments and her nephew who had also tested. I match him at 809 CMs across 31 segments as predicted 1st cousin also. We all agree I am related to her as a her half sister or she is my half aunt (making him my half nephew or half 1c.) The “father” (her dad) has passed away, but his location and travels align with my mothers and she “remembers” him.

    another side note: This paternal family is middle eastern (where their culture does intermarry) so I wonder how that may distort DNA. He and the wife (mother of the half sis and gma of the half nephew) were 1st cousins (of other 1st or 2nd cousin parents).

    Our question is can we use the X chromosone to verify if she is my half sibling? Would it
    help to compare our raw data in GED Match?

    on the X – for her, I match genomic postion: 68411445-112741785, genetic distance: 31.89cM and number of SNPs: 3226 (23andMe predicted relationship – 1c, our guess – half sister)

    on the X for him, I match genomic position: 13867132-112741785, genetic distance: 90.59cM and number of SNPs: 8146 (23andMe predicted relationship – 1c, our guess – half nephew)

    If we are off base here, is there another way to prove if she and I are actually half sisters or if she is my half aunt or (even half cousin – if another male family member (like brother to this presumed dad) is possible.

    Some things to consider. This culture (middle eastern) intermarries. This family my presumed BF married his 1c on her maternal side. This presumed half sister is their youngest daughter. The presumed nephew is their grandson (his mother is their oldest daughter). I am wondering if I should try to test with the oldest daughter to be certain.

  111. She is not your paternal half sister since you do not have a full X match, see post above. Sisters sharing a Dad will always share a full X. so either she is your maternal half sister or your cousin or aunt.
    Does she or her father have any brothers that can be tested? Or their children?
    I am offline this weekend but if you all upload to Gedmatch, you can look at segment sizes to help with this. I cannot look until Monday but will email you then. See

  112. Thanks for your response. She is not on my maternal side. She is definitely on my paternal side. Her dad (presumably my dad) died two years ago. This family is Palestinian. My mother is African American. I have my mothers results, she is zero match to any of my maternal matches, but IS a aunt to my 23andMe predicted first cousin match (who we think is my half nephew). I am going to test with his mom (her sister). I really feel SHE may not be the daughter of the man she knows as her dad (that I feel is my dad) so I am trying to tread lightly. Her parents were 1st cousins on their maternal side (acceptable in their culture- and also happened between their parents). She does have brothers, and perhaps one MAY be willing to test. I am trying to let her suggest who because I am not trying to disrupt this family. My mom and I only share about a 95% X. So I wasn’t sure if due to the intermarrying of her family and their genetics if that could be the issue. Her nephew has enough to be my half nephew at 810 cMs, so I hope to test with his mom (her sister).
    She has requested her raw data for Ged Match, however she tested after August (kit submitted in Sep 17, received Nov 17), so would she be able to use GED Match or would she need GED Match Genesis?

  113. How could we tell if we are related on her father’s side. We are thinking maybe we are related on her mother’s side. How could we tell?

  114. I have found a paternal 1st cousin. She was adopted. We match on the X chromosome along with most others. How can I tell if her parent was my paternal aunt or uncle?

    • In order to tell which side of the family she is related on, you need to see if she matches any cousins on your maternal or paternal side. If you do not have any tested, talk them into it!
      Because you are bothe women, the X is not that helpful. However if you match for the entire X you are most likely half sisters with the same Dad not cousins. There is much overlap in the amount of shared DNA between the two, I will send you an email.

  115. I have a shared segment of X chromosome DNA that’s 43.14cM with a male who by family history should be my 4th cousin; our mothers are likely 3rd cousins, and this male and my mom share a similar X segment that’s 42.93. Our families want to determine the common ancestor and can trace our lines back to 2 “sisters” born in the mid-1800’s but we don’t know if they were full or half sibs, and if they only shared one parent whether it was their mother or their father. How should I start to analyze the data further and do you think it’s possible to get answers from it?

      • Thanks! I just created a list of all the shared X segments. I’m able to compare several people who descend from my great great grandmother (Sarah) to the male match I described earlier, Andrew, whose great great grandmother (Chasha) was the full or half sister of mine. It looks consistent, that my mom, her 2 female first cousins in that line, my brother, and I all share some of the same X DNA with Andrew. I haven’t been concerning myself with the autosomal DNA for this match, and like you say, it’s not impressive. I’ll try reading up about the Y testing since I know nothing. I very much appreciate your help.

  116. If two maternal first cousins (male and female) marry, and have kids, how can the X chromosone still be so intact for the male to pass to his daughter? whats to say the recombination of the x (male got from his mom) chromosone does not intermix with the female (mother (also his wife) x chromosone, that came from the same female x chromosone (grandmother/aunt?)

  117. Towonia
    Recombination takes place in the parent not in the child.
    A daughter will have two X chromosomes. The one from her Dad did its recombining in the Dad’s mom. A female child of those cousins will have many fully identical regions on their pair of X chromosomes but the one from Dad will be whatever he got from his mom.

  118. I read this a couple of times and I am as confused as ever. So my dad and 2 siblings, 1 male(JP), 1 female LR). I think that DAD and LR are full siblings and JP is a maternal half to them both. Using Gedmatch, Dad matches LR with 2734.3cM / X = 46.1 cM (largest 46.1), dad matches JP 2023.1cM / X = 103.1 cM (largest 67.9 cM),
    LR matches JP 1708.9cM / X = 117.7 cM (largest 66.7 cM). I’m looking at the x matching graphs and it’s not making any sense to me and I’m no closer to proving full siblings between my dad and LR. Autosomal chart says full siblings for dad and LR, BUT HOW DO YOU TELL FROM THE X. A deceased sibling (PR), we know she was a half sibling to JP, but not sure if she’s full or half with DAD & LR. I did a kit for her daughter (JH), she matches dad at 1514.3cM / X = 48.1 cM (largest 48.1 cM), she matches LR 1872.5cM / X = 145.2 cM (largest 73.3 cM), she matches JP 745.0cM / X = 10.2 cM (largest 10.2 cM). Again, looking at the graph all I see is ?????.

  119. I am trying to determine if my (adopted) kids are full siblings to each other (they’re supposed to be…..) There are three girls and one boy. Girls 1 & 2 match girl 3 and Boy. But G3 and B share NO X DNA at all.
    total cM cM onX Longest
    G1 G2 , 2523.6 cM, 196.1 cM 196.1
    G1 G3, 2678.2 cM, 196.1 cM 196.1
    G1 B, 2729.9 cM, 106.4 cM 55.1

    Is there a possibility that they all have the same father and that G3 has a different mother? I’m thinking G3’s bio mom could be the half-sister of G1, G2, and B as they all have the same mother. Their bio father did have a relationship of sorts. Or is it just that recombination thing going on? This is all new and I am trying to wrap my head around it. Tested my bio son and my husband and our results are all so expected and these just aren’t. Thank you to all the helpful folks!

    • They are all full siblings.
      Boys only have one X from their mom while girls get an X from each parent and as explained above, the dad passes the same X to each girl.
      Because a mother has two X chromosomes she recombines them to pass to each child. Therefore it is possible, although unlikely for a brother to not match his sibling AT ALL on his X. He just got different X from his mom than the sib did
      imagine his X is
      DDDDMMMMDDDD (where DD is from moms dad and mm from her mom) and his sib got
      in that case, no match

  120. I need help please? can you tell me if person is on my mother or father side Our x match start here
    8,897,753 and ends here 22,563,888
    cm’s21.3 snps

    • Margaret
      You cannot tell from a single match. You need other relatives tested from the maternal or paternal side to help figure this out. A woman gets an X from each parent.

  121. does this mean Donna and I are half siblings with the same father, but not the same mother?

    our x chromosome is Largest segment = 194.8 cM
    Total of segments > 7 cM = 194.8 cM Actual.
    The whole bottom line is blue!

  122. Kitty, it’s me again,
    I think both these people are my half siblings
    Jeremy 1962.8 largest seg 214.5
    Jezz and Kate:115, 214.5, 101, 141, 104, 111, 114, 112, 108 largest segments

    Donna 1923.1 largest seg 172.7
    Donna and Kate, our biggest segments are 227.6,172,131,112
    Donna and Kate’s x chrom is 194.8 cm.

    Donna and Jez Largest segment = 187.0 cM
    Total of segments > 7 cM = 2,083.8 cM
    32 matching segments
    larges segments for Donna and Jez 187, 119, 161, 130, 104

    Could you help us out?
    If I read this correctly we are half siblings, I think we all have the same father!


  123. Could you kindly help me.

    Female Adoptee ( F1)
    Born in 1992
    match a Female born in 1972 (F2)
    I know she comes from my birth fathers side because I found my birth mother
    F2’s mother did a test and F1 did not match so we are assuming F2’s father had a son he did not know about making F1 and F2 half aunt/niece. Does this look correct
    Gedmatch kits : [removed]

    • I removed the kit numbers since it is general policy not to publish them.
      F2 and F1 share no X so they cannot be paternal siblings and they would not share X in your scenario
      They share a total of 1180 cM which fits half aunt/niece relationship 88% of the time

  124. Kitty question I did 23andMe and was a first to second cousin match with my half brothers first cousin ? This makes me think my biological father is related to my brothers father? Could this be a fluke or am I on the right track? I then did AncestryDNA and found a new possible half sister but she shared no dna with the cousin of my half brother or cousin? Help

    • Connie
      So your 23andme half brother is maternal? Could your ancestryDNA half sister be paternal? That would explain this simply. Or is she also the half sib of your half brother?

      • My half brother is on my mother’s side as is his cousin, she is my brothers fathers sisters daughter. The other girl that is on AncestryDNA seems to be on my fathers side . I don’t know my dad , and she was given up and is looking for her parents. She didn’t match the cousin I match on half brothers side nor my half brother. How on earth would I match my brothers cousin? But my half sister doesn’t? It’s very confusing. We are looking for our biological families. I know my mother. I had my mother’s sister do ancestry to see if it helps us get answers. Any thoughts? Thank you for getting back to me.

  125. Trying to decipher our results to determine if my relative and I are half sisters with the same father or niblings. We did the testing through 23andMe and uploaded the data to GEDmatch Genesis. After reading your blog especially this one and the half sibling vs nibling I am still left a bit uncertain.
    Here are our one-to-one from GEDmatch:
    Largest segment = 100.6 cM
    Total Half-Match segments (HIR) = 2009.3 cM (56.0 Pct)
    Estimated number of generations to MRCA = 1.4
    54 shared segments found for this comparison.
    481942 SNPs used for this comparison.
    75.0 Pct SNPs are full identical
    Largest segment = 87.4 cM
    Total segments = 181.4 cM (92.6 Pct)
    3 shared segments found for this comparison.
    9827 SNPs used for this comparison.

    In your opinion would this be half or nib?

  126. Why do I match my maternal grandmother 159.6 centimorgans on the x DNA compared to my sister who matches her 62.6?

    • Tajma,
      That is due to the randomness of DNA recombination.
      Your mother has an X from each of her parents.those 2 X chromosomes are recombined in each egg she makes. Some may get more from one parent and some more from the other.

  127. Hi Kitty,
    I am confused. I tested at ancestry and received a paternal match with 1281 cm/40 seg. We both uploaded to gedmatch which says 1336.8 cm/23 seg. Four largest segments are 218.5, 174.1, 131.9 and 91.4. We also match on the X 190.1 cm. Would this be a half sibling or is there another explanation, she is only 6 years older than me. Thank you.

  128. My two sons, who are confirmed to be from me and my husband via…when I compare their X Chromosome, half is no match (understandably) but the other half is green all the way accross…an EXACT match for the second half of the 23rd Chromosome. Does this mean that they both got the same, un-recombined X chromosome from me?

    • That means they got the same piece of X from you where they match. On the other half, you gave them different X.

      A man has only one X from his mother so cannot be identical on two sides which is what that green bar usually indicates. I guess that when two males match each other they are given that green bar to indicate a full match, a good match.

      • Ok. So many full brothers only have a half match on half of the X chromosome?
        My boys just happen to be a full match on half of the X chromosome? Is that common?

        • Since men have only one X, any match there is “full” or not false. Perhaps showing the green bar is not best since there is only one copy of the X but that is how it is shown.

  129. I just got 23and me results 2 days ago. All of this discussion is brand new to me and after reading several websites I’ve just today even sorted out a few terms and think I’m ready to give the info needed to ask my question…we’ll see 😉 23andme identified who I always thought was an aunt as a half sib (not such a surprise, really). We share 28.6% dna and 45 segments. The total cM is 2131 with 21 of those 45 segments ranged from 50 to 146. 100% of the identities are “half”. Our X is full except for a very small segment. An error? Are we half sibs or aunt/niece? Thanks in advance for your time! Seems like you spend a fair amount of it answering ppl’s questions. So appreciated.

    • Lori
      Half sibs and aunts both share about 25% of their DNA with you so it is hard to tell them apart and 23andme may not be correct in calling her a half sib. Read this article
      Then copy the matching segments to a spreadsheet, remove those less than 7cM and total the non X matches, Then check the graph to see if you have an answer
      Is she expected your father’s sister? Paternal side have larger segments. What are the 4 largest segments?

  130. To add to my last comment for clarification, after reading ^ A lot of what I’ve learned is from the conversations on this blog between you and others. I just noticed two conversations above where someone asked a very similar question as mine and said the two shared 190.1 cm on the X chromosome. You said they were paternal half sibs. I told you my shared X is almost full and wondered if the small break was an error and therefore really full (meaning it would be a shared maternal parent, correct?) But with a total X cm of 167.25 I now wonder if the biggest surprise might be that it’s a shared paternal parent (assuming we are half sibs). To be specific, the X chromosome matches from 1 – 137255351 and from 142698669 – 155092794. Hope I’ve given the info you need!

  131. Wow that was quick. The total cM without x is 1962.98. She is expected my mothers sister. The 4 largest not including x segments are: 78.19, 146.70, 146.00, 86.32. I’ll go to your website and see what I can find. Thanks!

  132. Will have to set up the graph tomorrow. Hopefully my brain will be a little clearer then. I have been on a steeeep learning curve the last several hours! After reading your blog, however, my case looks to be in the maternal nebula-like region. You said “that if all other indicators are ambiguous, the sizes of the four largest segments can indicate which relationship it is, that half siblings will usually share between two and four segments over 100 cM. While this works almost all the time for paternal half siblings, it is a closer call for maternal half siblings versus niblings.” I have the 2 shared segments above 100 but this would have to be a maternal parent.( I cannot figure out how it could be otherwise.) meaning this fits the more difficult comparison. When I eyeball your visual, my 4 largest segments would appear to match the half mat. I will set it up tomorrow to be more precise than “eyeballing” it, but would appreciate your further input. Seems like it is still ambiguous. My full (we THINK, lol) brother is going to send a sample to 23andme this week. I assume this additional data will help this determination?

    • Are there any more people in your mother’s generation in her family who could be tested? That would be the most help. Else their children.

  133. Female tested on AncestryDNA, matching someone at 2nd cousin. The brother also has AncestryDNA done, and does not match the “2nd cousin”.
    Requesting uploading to gedmatch, but whats they best way to figure out if its maternal/paternal. 2nd cousin is adopted, does not know details at this time.

  134. Hello Kitty,
    I decided todo the 23andMe to find out ethnicity. To my surprise I have been matched with a half-sister I didn’t know about. I have been researching to see if this could be true. We match 2170 cM and 36 segments. I am female, and have found the X chromosome will match entirely if half-sisters share the same father. The X chromosome line matches solid until the the very end where it is only a tiny area that is gray. You really have to look closely to see the color did not continue into that small spot. Our X chromosome matched numbers are as follows: Genomic Position: 1-154282391, Genetic distance: 181.84cM, and Number of SNPs: 14565. Do you agree this would be half sisters, or is it possible because the small area at the end of the X chromosome is not colored, we are some other relationship? Thank you in advance for your help.

  135. I thought the blue line at the bottom for the 2 half sisters is what showed they shared the same X chromosome from their father? Yet the last example for the Mother and Daughter have a solid blue line also. With the 2 half sisters I don’t see even a sliver of red. With the last example there are 2 slivers of red. I have never known who my biological father is so I had high hopes from using dna testing. I have found some possible matches and have talked some of them into submitting their raw dna to GEDmatch. I have one match that is
    Chr Start Location End Location Centimorgans (cM) SNPs
    X 519,506 154,886,292 196.1 17,946
    —sorry I tried to copy and paste the chart also. There is a solid blue line on the bottom and just as in the last example on your page there are 2 slivers of red above the blue line. Or is there another comparison we should try? The second match, who thinks her mother may be my half sister, had these results :
    Chr Start Location End Location Centimorgans (cM) SNPs
    X 67,348,646 154,886,292 105.0 9,926

    The first match is slightly older than I am and the second match is around 10 years younger than I am. Could I be looking at a half sister and a niece?

    Image size reduction: 1/18

  136. My sister and I tested on 23andme. We have 2 female first cousin matches.
    First cousin Sue is our Dad’s sister’s daughter. We both have x matches with Sue.

    122093729 151997273 51.12 3372
    122354683 150798536 48.20 3196

    Lisa is also a first cousin match. She is unknown to us.
    Lisa and I match 1016 cM 19 segments, but no match on X.
    Lisa and my sister match 958 cM 21 segments, no match on x.
    Sue and Lisa match 461 cM 18 segments, no match on x.

    Is Lisa truly a first cousin? If she is the daughter of my father’s brother, shouldn’t there be a match on x?

    • The lack of X is never meaningful other than precluding a shared Dad between two sisters. However it does make it unlikely that she is the daughter of your father’s brother since he and your father would have to have gotten completely different X from their mother. Possible but somewhat unlikely.
      Lisa’s very low match with Sue suggests she is not a first cousin although that is just barely possible. Could she be your father’s half sister?
      Get some more cousins from your father’s different parent lines to test and see how she matches them …

  137. Thank you for the very interesting article.

    Please can you tell me, can you distinguish if a cousin is from the maternal or paternal side by using tools on gedmatch. i.e. Like you explain above for the half siblings.

    I ran the x on gedmatch and the blue line is broken, so not half siblings , I am fairly sure it’s from the paternal side but like to confirm if possible.

  138. my brother and I both did the Ancestry DNA test (with out knowledge of one another). As matches came in, we were matched close family (possible range- first cousins). Shared DNA- Shared DNA: 1,480 cM across 55 segments.

    Which of courses surprised both of us. We have now shared our data in GEDmatch and received the below results. Needles to say, still confused. Are we half siblings??

    Wish I could copy the actual chart, but I’m unable to for some reason.
    Below is the information provided.

    Minimum threshold size to be included in total = 700 SNPs
    Mismatch-bunching Limit = 350 SNPs
    Minimum segment cM to be included in total = 7.0 cM

    Chr Start Location End Location Centimorgans (cM) SNPs
    X 41,472,162 99,630,571 39.7 4,493

    Any help you can provide will be very much appreciated

  139. Monica –
    The total cMs are too low to be full siblings. Since you share X, most likely you have the same mother but different fathers.

        • The strange part is that there are 4 of us (and he is the 2nd child born).. I’m the 3rd.

          So that would more than likely mean that there was another man involved during my parents marriage. We resemble each other (probably from my mom) but in looking at my dad’s pictures (he died when I was 6) and his family, it looks like my brother does not resemble my dad’s side of the family. My oldest brother does not want to take a DNA test (I tried to get him to do it). My youngest brother passed 20 years ago. I suppose I can have one of my uncle’s (dad’s sibling) take the test to determine which one of us is the one with a different father.

          • Yes, testing your Dad’s brother or any of his children would resolve this as they will probably only match one of you

  140. Dear Kitty,

    I recently added this question to your Sibling vs Nibling post but wondered if this was the more appropriate post as it’s regarding the X chromosome. My 82 year old mother in law has been searching for family most of her life with no results. She recently had a “close family” match pop up at Ancestry. She and the match (female, 75 years old) uploaded to GEDmatch. They share 1466.4cm across 33 segments. GEDmatch estimates 1.6 generations. When I utilize the x dna comparison tool it shows that they share an entire X chromosome with segments > 7cm = 196.0. Using the one to one tool I see 1 chromosome > 100cm, the #2 @ 109.4. I have learned from your Sib vs Nib post that paternal sibs usually share 2 or more chromosomes > 100cm. Does the x at 196 count as the second chromosome? Does sharing a full x trump how many shared chromosomes they have and make them half paternal sisters regardless? Thank you so much for your blog and the time/effort you put into it.

    • Thanks Tammy, I answered over there. The entire X makes having the same Dad by far the most likely thing. Very very rare to see that in any other relationships unless they are from endogamous populations.

  141. I am adopted and just found a half brother through 23andMe. I am a woman and we have over 50% identical DNA on the X chromosome. Does this rule out a shared father?

  142. Hello Kitty,
    I uploaded to FTDna from Ancestry. So far I can only identify two 4th-6th cousins or closer that are also on Ancestry.

    One female and I share 18.21 Cms / 1700 SNP’s on the X-chromosome.

    I know from my Ancestry work she is on my maternal side, and on one side of my tree from other closer matches.

    Can I theorize she and I share the same MRCA, or is it possible that some of the X is coming down another line? The male X inheritance seems so much easier!

    For comparison FTDna says we share 106 cms/16 segments, where Ancestry shows 57/ 4 segments.


    • Brian –
      It is always possible that one segment of X can be from a different line and can go back pretty far in time because of not being recombined when passing through a male.
      Family Tree DNA counts many small segments. Best to cut and paste the table of segments to a spreadsheet then delete all the ones smaller than 7cM and total the remainng ones. Then use the DNA painter calculator

  143. Thanks Kitty.
    I took the blank 5 generation X chart for females and built back for both her and my other X match that is also in my family tree on Ancestry. Because I know where they both are in my tree I have both their list of ancestors. That is an interesting exercise. Fun as well. Simple, but helps you visualize just where the X is coming from.

    The charts show that as you suggest, one is from one side of my maternal ancestors, and the other is from another side, so different MRCA’s. Both are five generations to our MRCA.

    FTDna allows you to sort in the chromosome browser, 1, 5, 7 and 10 cms, so it would be pretty easy to do as you suggest.

    Because of the extensive tree I’ve built I know where quite a few of my matches on my maternal line sit. The difficult thing is of course, trying to figure out where I fit in the thing.

  144. I can’t get my head around why a mother and daughter in your last example would match on the whole X chromosome. If the daughter gets half from each parent, wouldn’t she match only half with her mother, and the other half with her father? Then it occurs to me my problem is in understanding the blue line, and that is is only for half the chromosome pair, in this case the half the daughter shares with her mother. That leads to another thing I’m wondering given a bit of small town endogamy in my family. If my match and I have connections through both of my parents, might the blue line show one segment where we match on my father’s side and another where we match on my mother’s on the same chromosome?

    thanks, Lynn

    • You are forgetting that we have 23 PAIRs of chromosomes. So you get one full X from each parent if you are female. Plus the X from your mother is a recombination of her 2 Xs.

      Yes you can have one segment from your dad and another from your mother matching someone, when you are related to them on both sides, but you are unlikely to have a solid blue line with anyone but a close relative

  145. Two female first cousins of my dad are trying to determine if they are half-sisters or first cousins to each other. Cousin A was adopted but learned the identity of her bio parents and met her bio father before he died. Her bio dad was my dad’s uncle F. Cousin B learned through dna that her bio dad was someone other than the man that raised her. Her bio dad is either my dad’s uncle F or uncle J (also deceased). The time and place fits both uncles for both girls and both men were known to have borne children out of wedlock. There are presently no known descendants of either uncle who have done dna testing. Using an Ancestry kit, the two girls share a maddening 1255cm per GEDmatch one to one. They share two chromosomes in full and they have two segments over 100cm and one at 97. They share a full X chromosome. All queries were run with ‘Prevent hard breaks’ checked. Is it possible they are first cousins and each of their father’s inherited the same X chromosome from their mother? Or is the evidence strong enough to conclude they are half-sisters?

  146. It sounds like they tested on different versions at ancestry? It would be good if they tested again on the same chip version at the same company. That is likely to be more conclusive.

    I am 99% certain that they are half siblings based on the full X and the three very large segments.

  147. HI Kitty,
    As I understand it, an X chromosome comparison between half brothers that share the same mother will closely resemble the comparison between full brothers with the same mother.

    If we upload to our Ancestry dna to FTDna, the comparison of our X chromosome on their browser should show this fairly easily, correct?


  148. Yes the X comparison at ftDNA will be similar for half brothers and full brothers, but it may not be useful because on rare occasions the mother gives completely different X to each.
    If you are trying to determine which parent the half brothers share and they have no X, a 23andme test might help since it gives paternal and maternal line haplogroups. If only one of those is the same, you have your answer.
    If you are trying to determine if they are half or full, then upload to gedmatch genesis and look at the FIRs as per
    23andme also shows the FIRs

  149. Hi, I have just discovered that my mother and aunt are only half sisters.
    I have linked a picture of their X-DNA One-to-one Comparison
    It seems pretty clear that they don’t share the same father but what does the small bit of blue mean?

  150. Three years ago I tested my DNA. I matched a 1st cuz(no. 1) with an Anglo surname. The Cm numbers were in the 740 range. He put me in contact with his Cuz(no. 2). He had his DNA tested and they match me as a 1st cuz also, the cm were in the 1050 range. Their grand father had 3 sons. 9 months before I was born 2 of his sons were serving in France during wwII. That leaves Cuz no. 2 father as my father but the cm numbers are lower than the charts list a 1/2 brother. Can this still be possible?

  151. Hi Kitty, I’ve had another one of my Aunts DNA tested and I’ve compared her DNA to my mothers on several sites to make sure they’re full sisters. It shows that their shared DNA is in range but a bit on the low side for full sisters. MyHeritage says 2,364.4‎ cM which is low but in range, GEDMatch says 2382.7 cM in one-to-one compare which again is low but in range and then FamilyTreeDNA says 2,239 cM which DNAPainter says it’s 53.71% Chance that they’re half-siblings. They’re a full X-Match though so I’m pretty sure that means they’re full sisters. I did have a thought though, what if they are half-sister but their fathers are full-brothers, would they still be a full X-Match?

  152. Hi Kitty I am big into the ancestry tree research and did DNA testing to learn more and help me with our family tree. My sister and I tested with 23 & me and AncestryDNA. And no idea we were going to open up a can of worms…
    In AncestryDNA it shows us sharing 1703 cM, and she shows ancestry 50% European Jewish, and I show 47.1% Italian. On my AncestryDNA I have a 1st-2nd cousin with 727 cM, and 4 1st-2nd cousins with 494 cM, 474cM, 437 cM, and 363 cM. Which do not show as matches on my sisters AncestryDNA testing. My sister also is showing an Aunt and 1st cousins in 23 and me, that do not show on my 23 and me testing results. I know this leans towards us being half siblings. Is there any chance we could still be full? And if not, how do we determine which one has a different dad without asking mom? Our mom and dad were divorced when we were young, but we have always been very close sisters and will still be, no matter the outcome. Now I don’t know if my family tree is accurate. thanks in advance for any input you can provide.

      • Hi Kitty –
        Just to add, our dad was an only child. However, his dad did have 2 siblings. We are trying to convince our brother to do a test with 23 and me. is it worth us to pressure him to do so?


        • The people you want to test are the descendants of you grandad’s siblings to see if either of you are related.
          Of course you want your brother to test but that is his own decision to make. Tell him why. Perhaps he has a different dad too.

  153. This x has me totally confused, just when I think I have a good grasp I read another question and response and I am back to square one. I am an adoptee with no clue as to bio family. DNA testing has been great and although I am not even close to determining my identity I have lots of new DNA cousins. My Question: Based on DNA I am the offspring of 2 ethnicities – the x-match indicator only appears on matches from one ethnic group. What can learn from this?

    • Since you are female, you get X from both parents so there is nothing you can learn yet. You might learn more from your mtDNA haplogroup which only comes from your maternal line. You can get that with a 23andme or living DNA test. Many of those are more frequent in specific ethnicities.

      Please read my page for adoptees and be sure to test everywhere

  154. My maternal grandmother was given up to a state home when she was 4 years old. I have been able to determine her paternal heritage, but her maternal heritage is still a mystery. My mother is no longer living, but her sister did an Ancestry DNA test for me. That is the only link we have to finding my maternal grandmother’s maternal heritage. My aunt’s DNA info has been uploaded to GEDmatch. Is there a way to find matches that are related strictly on the maternal side? I am open to help if anyone has the knowledge to help me solve this mystery.

    • Amy –
      Are any close relatives on your grandmother’s father’s side tested? Can you get someone to test? That is the best way to separate the sides- maternal matches will be the ones who do not match the paternal relatives. Another way to separate is if the ethnicity is very different.
      Get your aunt’s test on every other web site and have her test at 23andme as well.
      Use the techniques adoptees use. See

  155. Yes, I did locate the 92 year old daughter of my grandmother’s half brother (same father). I was fortunate enough to meet her and have her complete an Ancestry DNA kit. Her results have also been uploaded to Gedmatch.

    • The X for two half sisters sharing the same mother can be anything from 0 to 100% just like any other chromsome. 75% sounds just fine.

      One thing that MUST be identical, however, with a shared motehr is the mtDNA haplogroup

  156. Hello Kitty.
    I tested on Ancestry DNA and uploaded my DNA into Gedmatch to see if a close match was a half sibling, aunt, or niece. (Too close in age to be my grandparent) Our DNA matched at 1528 CM. Our GEDMatch results show a line with green and yellow pinstripes all the way down, with a solid blue line at the bottom. Would this mean we share the same dad?

  157. ‘m being told by someone on DNA Detectives that anything under 10 cM’s on the X cannot not be seen as accurate. Is that true?

  158. Dear Kitty,

    Thank you so much for your blog. It’s been so helpful to me as an adoptee. I’m now trying help a friend solve the mystery of a close family member who popped up on Ancestry.

    Total shared CM 1750

    X chromosome shares full blue bar on
    GEDmatch/190 cm

    Chromosome 1- 107 CM
    Chromosome 4- 122
    Chromosome 9- 123
    Chromosome 11- 124

    36 shared segments
    59.4 fully identical

    Wondering if the full blue bar on the x indicates paternal half sisters?

    My friends match was adopted out of Portland. My friends father lived in Portland and her brother visited regularly to see their father. Could we distinguish between half sibling or nibling using that fully shared x?

  159. Hi I’m trying to determine between half paternal aunt/nice and half paternal sisters

    They are 1437cm on Ancestry.

    I did a one to one X on Gedmatch and there is a gap on the blue line which is about 3/4 of an inch big and then a tiny sliver of a gap further along of black. When I tick the box “Prevent Hard Breaks (default is to create hard breaks when distance between SNP’s exceeds 500,000 base positions):” the larger gap of black disappears and it just leaves the tiny sliver of black.

    Largest segment = 82.7 cM

    Total segments = 180.3 cM (94.919 Pct)

    3 shared segments found for this comparison.

    Chr B37 Start Pos’n B37 End Pos’n CM SNPs
    X 2,700,157 52,067,217 82.7 4,498

    X 77,372,275 123,550,544 42.8 2,808
    X 123,953,559 154,892,230 54.8 2,728

    I know that the blue line should be solid but I did my own with my full sister and we have a tiny sliver of black too so I want to be as sure as I can be.

    Can you help?


  160. Follow on from my previous message regarding determining between paternal half aunt/nice or paternal half sisters::

    This is the reading after I tick the box that says “Prevent Hard Breaks (default is to create hard breaks when distance between SNP’s exceeds 500,000 base positions):” The blue line is solid apart from one tiny sliver of black. Is this a processing error or does it prove half aunt/niece?

    Chr B37 Start Pos’n B37 End Pos’n CM SNPs
    X 2,700,157 123,550,544 134.4 8,000

    X 123,953,559 154,892,230 54.8 2,728

    [I would also like to clarify that the tiny sliver of black that I have when I compare my full sister and I disappears when I tick the box that says “Prevent Hard Breaks (default is to create hard breaks when distance between SNP’s exceeds 500,000 base positions):” ie my x blue line is solid with my full sister]


  161. I share X DNA with a female dna match. Our shared dna is 27cm over two segments. We have already established a common ancestor. My great grandfather and her great great grandfather were brothers. We also have shared matches who come from the same common ancestor. My problem is as my lineage back to our common ancestor is three males, being my father, my grandfather and my great great grandfather how is this possible

    • You must share another common ancestor with her. X can last a very long time so it could be further back than you have looked or can even find.

  162. I am trying to learn genetic genealogy, sometimes it is just Greek to me! I came across a very odd X match. My sister/D and I/L and a girl/B half our age with the X cm amounts D=89.88 (a break) 96.71 L=195.93 and B=195.93. The B (girl half our age) is 5th to Remote cousin at 35 cm, 10 segments and the largest 9cm. Oh, these are matches on my mothers side, under her name in FTDNA. Is this odd to match like this? I reached out to her and was told her mother is adopted and her father passed away. My Mom is adopted as well and I do know her birth mother side for sure. She knows her birth father side for sure. I did ask for her to upload to Gedmatch with no reply yet. I was just wondering if you have ever seen this before? Thank you

  163. I am a female, my father was adopted by his aunt. My father passed away 3 years ago at age 89. He was told, at age 17, who his mother was, and a last name of his father, who had apparently passed away by that time. I have had my DNA test, as has my mother, sister, daughter, niece, brother and cousins on my mothers side.
    I have been hoping to find my paternal grandfather’s family. Most of my matches are to my mom’s side. However, I was surprised to find a niece I never knew I had through which I learned of a half sister (her mother) I never knew I had. As it turns out, my dad had another child he was keeping secret for nearly 70 years. My half sister does not know about me. Now, I am able to see my half(?) niece’s DNA matches and those we share.
    I would like to know how to narrow matches down to my paternal grandfathers side. I can recognize most matches to my paternal grandmothers side. Should I be looking for who my half niece and I both match? Should I look more at 3-5 cousins? Any advice would be appreciated? Would “x” matches be helpful? Thanks Sincerely, Mary

  164. Hi Mary,
    Yes you want to look at the matches you and your half niece share but many of them will be to your father’s mother’s side. You need to build her tree well so you can tell which matches are to your father’s father.
    You will not share any X with your father’s father’s descendants since X cannot pass through 2 men.

  165. Please forgive my ignorance — watching videos and reading articles but so confused ! Seeking help confirming half sibling. If another female and I compare our x dna with the one to one comparison tool and the results are a graphic that is all yellow and green across the top with a blue bar underneath (except for one small black break), and we share a total of 1915 cMs — does this mean that we share a father?

  166. From your article — “If they had the same father you would see a solid blue line as shown below in the made-up example of two half sisters with the same father.”
    My probably half-sister and me (a female) have a small black break – does that change the conclusion?

    • JoGe
      You need to check the box “prevent hard breaks” – that will get rid of the small black break if you share a full X
      Women with the same father will always share a full X so a solid blue line on the X one to on. However there are rare cases where half siblings with the same mother share a full X, but I have only ever heard of one and that was from an endofamous population.
      In other words, if you not share a full X then you o not share a Dad but when you do share a full X it is only 99% that you share a Dad. I have never seen an aunt/niece relationship sharing a full X but it is theoretically possible. So please look at other indicators to be sure

  167. Hi Kitty,

    A 2nd-to-3rd cousin found me on 23andMe and I agreed to try to help her find her birth father. Her mother put her up for adoption at birth. Her dozen or so triangulated matches with me (180 cm) and a close relative (~324 cm) include DNA from two lines in my family that converge with my great-grandparents. I’m fairly confident that one of her parents is a descendant of my great-grandparents, but how can I tell if that parent is her mother or her father? Can X-chromosomes help? What other methods might there be for separating her maternal and paternal matches given that she has zero genealogical info on the paternal side, nothing but her birth mother’s name and fuzzy grandparents on the maternal side, and no DNA matches from known relatives other than me and my relative?

    With Thanks,


  168. John –
    Great of you to help. X occasionally helps but it is not the go to item. Nor do we worry about which parent is your relative initially.
    I have slides from a presentation which you might find useful here:
    Make sure she has her non id information if her original birth certificate is not available
    Typically you would build the tree of all the descendants of your great grandparents down to the time of conception looking for someone who was about the right age and for whom there are possible matches on the side of the parent not related to you.
    Also look at this page of resources, particularly DNAadoption
    Make sure she has her non id information if her original birth certificate is not available as that may have geographic and other clues

  169. I’m looking to find out if 23andme is right about a match. I’ve never known my father. I took the DNA test and it came back as a 20.16 % match with a woman. I’m not sure what is considered a full X match. We share 181.84cM on X chromosome. She also has an uncle. Would I more likely be half Sister or first cousin?

  170. Hi Kitty,
    My friend ‘Nancy’s’ biological father is unknown. At 23andMe, Nancy matches ‘Jill’ at 970 cM. Nancy was born in 1969 and Jill was born in 1988. After some research, it appears the relationship is 1/2 Aunt/Niece. Nancy and Jill share no xDNA. If the 1/2 Aunt/Niece relationship is correct and since Nancy and Jill share no xDNA, can I safely assume that Jill’s Dad (not Jill’s Mom) is likely Nancy’s 1/2 sibling (and they – Nancy and Jill’s Dad – share a father)? Thank you.

    • You cannot assume from the lack of an X match since occasionally a mother passes the entire X from one of her parents to a child.

      However since X does not pass through 2 men, your assumption is highly probable, but it could be either parent of Jill’s … maybe 95% that it is her dad…

  171. Hi, if I know for sure who my mother was, if I get a DNAmatch for a half sister would we both have the same father?

    • Once you know who your half sister is, double check that she is a sister not an aunt or a niece as mentioned above. Also double check that she is not a half sister via your mother …

  172. KItty: You are a great resource. I am still confounded with a discrepancy that prevents me from having confidence in predicting whether a Male “?” was my biological great grandfather.
    i am a male. I match with some brother and sister pair who are known to be the great, great grandchildren of Male “?”. If “?” is truly my great grandfather I believe that I should match with both brother and sister as half 2nd cousins, 1X removed. I match with the brother at 159cm but with his sister at only 48cm. Interestingly, I do not match with the sister on my X chromosome but share two segments (9.4 CM and 4.64 CM) on my X chromosome with the brother. If “?” was truly my great grandfather, the line would have been through him to my grandmother to my mother to me. For the X-matched brother, the line went from “?” to a great grandmother to a grandfather to a mother to him.
    Any confidence here that ‘?” is my great grandfather based on the matching results with the brother/sister and do the X chromosome results give me any more confidence in the prediction (outside of the fact that the brother and I share my maternal line)? Sorry for the lengthy narrative. Can’t find an answer to this in my research.

    • Get more descendants of male “?” to test if you can. Also drop the SNP threshold on the X comparison to the sister (GEDmatch only). See if you actually match … Those numbers are fine for 2C1R but the best way to confirm is more data!
      Another way to confirm is to find a cousin in your family on the male only line from “?” and the same in the other family and test the Y

  173. Hello, I have a question. I did 23andme and my first cousin on my dads side (our dads are brothers) had already done it prior to myself. Results came back with 20.22% dna shared and 1505cM however for the X chromosome there is a tiny portion at the top and tiny portion at the bottom we don’t share. 23andme listed our predicted relationship as half siblings but this has to be impossible correct?

    • You are correct. If you had the same Dad you would share an entire X.
      The amount of DNA you share has not been observed for first cousins but the probability table says a 1% chance. Men do not divide up their DNA for reproduction into as many pieces as women and I have seen larger amounts shared between first cousins whose fathers are brothers.

      Could your mother’s be distantly related? Or are you from an endogamous population?

  174. Hi, I have been reading and reading about how to interpret my siblings and my dna results. I am stumped and need some help! So my father before he passed said he may not be my father, but my uncle (his brother) might be. So we all did ancestry dna and here is what it says:

    me to my sister: 2294cm shared
    me to my brother: 2309cm shared
    my brother to my sister: 2526cm shared

    now X-DNA

    me to my sister: 98.8% there is a black segment 187.8cm – lrg seg 105.1
    me to my brother: 0% whole line is black
    my brother to my sister: 58.1% about half and half black/blue 110.4cm – lrg seg 65.1

    What does this mean, I can’t find anything about why a brother and sister wouldn’t share at least some X like my sister and brother do?

    Thanks for any and all input!

  175. It is certainly possible although unlikely for a brother not to share X with a sister. Their mother would have had to pass different X segments to each of them.

    Two sisters with the same father should share a full X but there a section in the middle which will be black unless you check the prevent hard breaks box.

    Finally read this article to see more about sibling matching

  176. My supposed uncle from side:
    1869 cm 38 segments
    180.0 cm X

    In my Heritages it says uncle I think because of the age he put …I been tipped that there’s a possibility that neither of my parents are my bio parents hence I took a DNA test.. also their avoidance and lies been thrown around….cutting it short I am fine with it just trying to find out to whom I am related and how am I related to him … any ideas I would love to hear I don’t really know but uncle does not stick, thank you so much

  177. He could ba your uncle but with that large an X match, half brother or maternal grandad more likely… build his tree and look who else you both match to try and figure it out. Use the techniques described under help for adoptees here

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