How to tell the relationship from the shared DNA

Many people have the illusion that if their testing company says a person is a 3rd to 5th cousin they really will be. That is not the case.

The testing companies are just making the best guess they can from the data they have. They do not seem to take segment sizes into account, rather they primarily use total shared DNA measured in centimorgans (cMs) for their relatedness estimates, usually the sum of all matching segments of 5 cM or larger. Close relatives will always share larger chunks with each other and so size does matter here.

Recently I have received numerous questions from people trying to figure out if a new match is a half sibling or a niece or a grandchild. These are hard to tell apart without testing more relatives as they all share about 25% of their DNA with each other. So I decided to collect some detailed statistics on those specific relationships with a google form (click here) that includes total segments and segment sizes for a future blog post [UPDATE as of sept 2017: First round results are written up at https://blog.kittycooper.com/2017/09/the-25-relationship-a-first-look-at-the-data/ ]

The companies predict reasonably well for close family but it is just not possible to be accurate beyond that due to the randomness of DNA inheritance.

For example, here is a picture from the new 23andme of some of the DNA I share with Dick, a 2nd cousin on Dad’s paternal side so blue, and John, a 2nd cousin on Dad’s maternal side so red.

Ktty2ndCousinsS

I share a third again as much DNA with John as I do with Dick,  even excluding the 14 cM on the X. The expected amount for a 2nd cousin is 3.125% which is 212.50 cM, right in the middle between these two.
Henry2nds Checking my brother, I see the same effect – he has 282 cM with John versus 185 with Dick. Not surprisingly, when I look at Dad I find that he shares almost twice as much with John as with Dick. Clearly he just inherited more of the same DNA as John’s mother from their common grandparents. Conversely, he inherited less DNA shared with Dick’s mother from his other grandparents.

On the left is a comparison of my first cousin Henry with both Dick and John. The amount he shares with each 2nd cousin is practically identical, as long as you subtract the 40 cM that he shares with John on the X from the total shown by 23andme. Amazing how variable DNA inheritance can be among 2nd cousins.

Click here for the ISOGG wiki article on Autosomal DNA statistics which usually includes the current chart from Blaine Bettinger’s shared centimorgan DNA project.

Personally I have his chart (shown below, click it for a larger version) bookmarked for easy reference. I rely on it heavily.

SharedcMProjectSmll

Warning, Ancestry.com DNA testing will show a smaller number of matching cMs and larger number of segments due to their algorithm which removes population specific segments.

The DNA adoption site has a relationship calculator that can help figure out closer relationships discussed in the article at Roberta’s blog called Demystifying Ancestry’s Relationship Predictions Inspires New Relationship Estimator Tool.

Autosomal DNA matching is not cut and dried due to the randomness of DNA inheritance and is even more confusing if you are from an endogamous population because your parents will likely share some DNA due to ancestral cousin marriages. Thus a match could be related on both sides! There is a function on the GEDmatch site that lets you check if the parents of a specific kit are related because they have passed along matching DNA segments.

I have sometimes found that someone predicted to be a 3rd/4th cousin based on total cMs is much more distant. This has happened when there are two good sized matching segments but each segment is from a different ancestral couple. Thus the relationship is much further back, for example, a double 6th cousin.

Another issue is the fact that the testing companies cannot tell which of the two paired chromosomes a match is on. So when you have a match that neither parent has, it is a false match created from small bits from each parent by the computer program (see my IBC article). This is why I prefer to look at matches that are “phased” that is to say a child and a parent have the same match.

If you only match someone on a single good sized segment (greater than 10 cM for most, more than 20 cM for the endogamous) your DNA relative can be anywhere from a 4th to a 14th cousin. See http://ongenetics.blogspot.com/2011/02/genetic-genealogy-and-single-segment.html?m=1 for a further discussion of that.

UPDATE 10/17/2017: There is now an easy to use online calculator based on Blaine Bettinger’s lastest chart at: https://dnapainter.com/tools/sharedcm that will show you all the possibilities for the shared cMs. Then you can use the ages of the testers plus test more relatives to try to figure it out.

Last but not least here is my data collection form which you can fill out right from this blog post (use the slider on the right to scroll down it to answer all questions).

81 thoughts on “How to tell the relationship from the shared DNA

Click here to add your thoughts at the end of the comments
  1. Thank you for this! 🙂 Especially with the half-sibling vs. grandparent to grandchild or aunt/uncle to nephew/niece relationship, which are all difficult to tell.

  2. In my project using 23andme comparisons there is a difference in segment counts for one relationship vs another.

    Grandparent-grandchild from 23 segments to 37 segments. The 37 segments is an outlier with 3 X-chromosome segments. Grandmothers appear to share a couple of more

    Ethan vs. Robert, 21.9%, 1629 cM, 23 seg (zero X-chromosome)
    Ethan vs. Janice, 25.4%, 1892 cM, 26 seg (zero X-chromosome)
    Ethan vs. Rocky, 22.0%, 1638 cM, 24 seg (79cM X-chromosome, 2 seg)
    Ethan vs. Vivian, 28.0%, 2082 cM, 37 seg (103cM X-chromosome, 3 seg)

    Kalea vs. Robert, 24.1%, 1792 cM, 25 seg (zero X-chromosome)
    Kalea vs. Janice, 25.7%, 1909 cM, 26 seg (full X-chromosome, 182cM)
    Kalea vs. Rocky, 28.1%, 2089 cM, 23 seg (full X-chromosome, 182cM)
    Kalea vs. Vivian, 21.9%, 1631 cM, 25 seg (zero X-chromosome)

    Shay vs. Robert, 21.8%, 1625 cM, 23 seg (zero X-chromosome)
    Shay vs. Janice, 28%, 2085 cM, 24 seg (full X-chromosome, 182cM)
    Shay vs. Rich, 19.7%, 1466 cM, 24 seg (full X-chromosome, 182cM)
    Shay vs. Marcy, 30.1%, 2236 cM, 29 seg (zero X-chromosome)

    1/2 sister vs. paternal 1/2 brother, 26.6%, 1978 cM, 32 seg (share no X)
    1/2 sister vs. paternal 1/2 sister, 29.2%, 2176 cM, 35 seg (share full X, 182cM, 2.45%)
    1/2 sister vs. paternal 1/2 sister, 23.0%, 1713 cM, 31 seg (share full X, 182cM, 2.45%)

    Paternal aunt vs. paternal nephew, 26.7%, 1984 cM, 46 seg
    Paternal aunt vs. paternal nephew, 26.2%, 1946 cM, 46 seg
    Paternal aunt vs. paternal nephew, 24.9%, 1850 cM, 42 seg
    Paternal uncle vs. paternal nephew, 21.7%, 1611 cM, 46 seg
    Paternal uncle vs. paternal niece, 25.0%, 1857 cM, 55 seg (includes 2X seg, 81.6cM)
    Paternal uncle vs. paternal niece, 24.5%, 1823 cM, 53 seg (includes 2X seg, 81.6cM)
    Maternal nephew vs me 20.1%, 1495.4 cM, 35 seg (includes 1X seg, 18.5cM)
    Maternal nephew vs my full sister 28.6%, 2127.8 cM, 40 seg (includes some completely identical X seg, 169cM)

    • I miss stated (completely identical X-segment), I was thinking about his mother and my sister sharing a large amount of completely identical X chromosome.

  3. Hi I saw your question posed on Facebook but wasn’t sure how to complete form properly so I’m happy to give you GedMatch numbers so you can take a look if you like

    Grandson (M4+1) A347430 and his Maternal Grandmother (M0) A903999
    Note Grandson’s paternal great grandmother is Ashkenazi/endogamic. Grandson is 8% European Jewish according to Ancestry.

    Nephew (M4+1) A347430 and his Aunt (M2) A219400
    Nephew’s paternal great grandmother is Aunt’s paternal grandmother. She was Jewish.

  4. Sorry I’m of no help, but I share 811 with a great uncle and 942 with a great aunt. When my mother gets her results in a few weeks, we will know how much is shared between her and her aunt.

    I did have a quick question. On 23andme, my great uncle got a little (0.1%) Sub-Saharan African. I was wondering if all the ancestors he has, I also have, but he doesn’t have all the ancestors that I have? And if he has African ancestry from a slave (as he has deep ancestry is from Kentucky and Virginia), would I also have that ancestor, just no Sub-Saharan African showed up for me on ancestry?

  5. The maternal or paternal question has now been added to the bottom of the form
    Please any of you who still have the window open so can edit their response, add that information. Anyone who cannot edi,t send me the answer with the total cM and aprox time and date when you added your numbers, thanks!

  6. Done – this was an interesting exercise. I provided information for me and my two brothers compared with my mother’s sister and my mother with my mother’s sister’s daughter.

    I also added my half brother, but that is from Ancestry.com (he hasn’t gotten around to doing more with his DNA – hopefully soon I’ll get him on GEDmatch).

  7. This is very timely as I am trying to figure out if my FIL has found an aunt or a half-sibling to his match. They match at 2009 cM with 45 matching segments, the largest being 199.3 cM’s. FIL was b. 1947 and the match was b. 1938, so this is probably not grandparent/grandchild relationship.

    We did not know of this family, I was looking for a different paternal family.

    The match has a nephew (a son of her sister) who matches at 1548 cM and 42 matching segments with the largest being 100 cM. The nephew was b. 1973. It is assumed that the nephew and the aunt are full matches, not half, but the nephews mom has not yet tested.

    The nephew matches my FIL with 747 cM’s and 26 matching segments, the largest being 77 cM’s.

    I am going to fill out the Google document for each. Thank you.

  8. Dear Kitty,
    Thank you for this helpful blog post. I recently uploaded my DNA to Gedmatch from Ancestry. I am adopted and know my birthmother. My half-sister will have her DNA results soon. However,I had an interesting match come up and using your Google form, it appears that the gentleman in question is either a half-sibling, Uncle, or Grandparent. I was surpised given that our shared cM’s are not that high- 59.8. Perhaps I filled out the form incorrectly. Thank you in advance for any thoughts on this matter.

  9. Hi Kitty. I have entered two grandparent/grandchild and six aunt/uncle to nephew/neice for you! Will be interested to see the outcome of this data analysis.

  10. I completed the form for my match with someone who we both grew up believing we were 1st cousins. Recent revelations have caused us to wonder if we might be half-siblings. Thank you for helping us.

  11. I took a DNA test in Ancestry . 1 girls on 50, one 52, and I’m 58 matched my DNA . They have 1600 and 1700 centrimorgans of mine. They were both adopted at birth. The one with 1700 centrimorgans said she found her birth mother before she died. She ask her who her father was and she said Dennis Williams, That’s was my dad. I knew then she must be my 1/2 sister. The other girl shares 1600 centrimorgans she was adopted at birth in Oklahoma City. We lived there too.
    They have 47 segments .
    How can I be sure they are my 1/2 sisters? I believe they are I can’t be their grandma, aunt , cousin etc,

    Thanks
    Cindy K

  12. Pingback: Relationship Estimates - Beneath the Cairn

  13. Hi Kitty,

    I’d done the Ancestry DNA as has my first cousin (maternal) and his father (my maternal uncle), but the “relationship” came up not as expected. My cousin matched with me at the level of 2nd cousin (293 centimorgans shared across 14 DNA segments) and my uncle matched at the level of 1st cousin (797 centimorgans shared across 35 DNA segments) which was my first hint that something was a bit off (on the other hand, a first cousin on my paternal line matched exactly as expected). So…I had my mom do the test. And she matched to her brother at the level of first cousin (1,761 centimorgans shared across 60 DNA segments). From my reading here, my assumption is that they are more likely to be half-siblings than full siblings (they are about 10 years apart). I’ve also read about looking for large segments of green on GEDmatch one to one compare and am hoping they will upload to GEDmatch so I can do so.

    My assumption is that they have different fathers vs. mothers as having different mom’s would mean my grandmother raised another woman’s child as her own…which I feel would be highly unlikely. But want to make sure I rule in and out every possibility before I present this info to my mom and uncle. My question is how I would be able to tell if they had different mothers vs. different fathers?

    • You are right that they almost surely have different fathers. If they both upload to GEDmatch.com, you could check their X, if they share a significant chunk or two then they have the same mother. However if they share no X, it is not a sure thing that they have different mothers, just about 98% or so (a guesstimate).
      Best is to compare each of them to their maternal and paternal side cousins to confirm which lines they match on. 2nd and even 3rd cousins will do for that.

  14. I have done the Ancestry DNA autosomal test a couple of years ago. I have noticed a trend of DNA shared with me of some of my cousins on strictly the paternal side and have compared the results with the DNA Detectives chart. The results have been for the most part, trending lower than the average cM shared as per the chart, going from my closest to the more distant known cousins..
    Examples: One cousin shares 975 cM across 42 segments which meets the charts average cM shared expectations – no argument there: A first cousin once removed shares 270 cM across 15 segments with me which is very low, compared to the average per the chart of 450 cM; a 2nd cousin shares 215 cM with me, which is below the average of 224 cM; A 3rd cousin shares only 14.1 cM across 2 segments and says I’m a 5th to 8th (distant) cousin which is absolutely not true and the average is supposed to be 56 cM; I also have a 3rd cousin once removed, who only shares 13.6 cM across 1 segment and says I’m a 5th to 8th cousin (distant) which is very low because 30 cM shared is supposed to be the average per the chart.
    It just seems like my paternal grandparents all the way back to my great-great grandparents (paternal) did not share much DNA down to me or my proven known cousins. Why??
    With this below average trend of shared DNA, is it possible that my 5th cousin and her Aunt would only share 4 to 5 cM with me, if I uploaded my DNA to Gedmatch? I would expect so. I did notice an online chart, similar to the DNA Detectives chart on that also.

    • Tony,
      DNA inheritance can be quite random after close family. I only got 22% from my maternal grandmother, rather than the expected 25%. As I discussed in the article one 2nd cousin shares twice as much with me as another but this did not hold true for my first cousins with those same 2nd cousins.
      After 3rd cousins it gets more and more random, so don’t read anything into it.
      However, do check of you have matches on all lines since another explanation for consistently sharing less is that they are all half cousins and there is an NPE up your paternal line.
      Finally, do be aware that ancestry removes pile up segments so their numbers can be lower.

  15. Is there any way to determine that this information from ancestry can definitely determine whither a person is a niece or a first or second cousin. From ancestry this person shares 418 cm across 22 segments. We know that she is my nephews child. When my grandmother was 41 and her oldest child(my mother ) was 13 she past of complications of uterine hemorrhage and my mother and her siblings we spit up in different states. My mother and my “sister” was the only ones kept together. Strangely my sister”s birthday is only days after her the date on her signed death certificate. We were wondering if my mom and sister are really siblings instead of mother and daughter. If they were said to be mother and daughter to keep them together. My grandfather ended up in prison about that time. My mother and her siblings are all dead. My sister was 27 years older that I am. My sister is my nephews mom.

    • Carolyn –
      This is a bit complicated of a story. Can you test your mother and your “sister”? If so, you uploading their results to GEDmatch then comparing them would tell us. But it sounds like you are trying to determine this from other tests?
      Your great-niece shares less than the normal amount of DNA for that relationship. But ancestry removes some matching segments so again, get those numbers fromGEDmatch. See this page for expected amount of shared DNA for different relationships
      https://isogg.org/wiki/Autosomal_DNA_statistics

  16. Me and my first cousin share 6.4 .But 23 and me says we are first cousins once removed.I beleave my grand father is my real father.And his mother is my half sister.I think thats why 6.4 not 12.Please help with all combinations.

  17. I’m a newbie, if this is the wrong spot to ask a general dna question, I apologize. I share 1153 cM over 36 segments with someone (Ancestry DNA test).
    How much DNA might we share if this person were the daughter of my half-brother and a woman who is not my mother? Or, the daughter of my half-brother’s son and a woman who is not my mother?
    I feel inadequate at this and I just bought you a glass of wine to thank you for answering such questions.

  18. I am a bit confused. There has always been a question as to my birth father. My father questioned my paternity and my mom denied any problems. I hope that my niece who is a match on ancestry dna at 1347 cM at 52 segments is my full niece . I would appreciate your thoughts as we only share 19% of our dna.

    Ps
    It also appears that some of my shared matches, match both my father’s mother side with my mom’s side.

    Thank you for your help and wonderful blog.

  19. Hello,
    A group of my family members (father, my 1/2 sister and her 2 kids, my aunt and her daughter) have done 23 & me. I looked at different pairs of relationships -total shared cm’s & # of segments to try and determine if the numbers seemed to make sense based on the closeness of the relationship. I don’t think they do make sense.

    My first question relates to my father and aunt. When I compare their data they share a number of complete cm’s, and a number of 1/2 identical cm’s. Is the total number of cm’s they share the sum of these 2?

    My second question, would my Dad and his grandson share any complete dna?

    My Dad was born 1st and my Aunt followed. I am wondering if my father’s father, is actually the man he believed to be his grandfather.

    Any feedback you could offer would be very much appreciated.

    Thank you

  20. Hi Jane –
    Make yourself a McGuire chart to look at the relationships. I find this most useful for clarifying them
    http://thegeneticgenealogist.com/2017/03/19/guest-post-the-mcguire-method-simplified-visual-dna-comparisons/

    To question 1: Normally just the half identical segment total is used. However 23andme shows you both totals in the comparison found at 23andme tools > DNA relatives > DNA. Warning, it includes the X and all segments > 5cM so some adjustments are needed to use this with the various charts.

    To question 2: Your Dad and grandson would normally not share any significantly sized fully identical segments unless his Dad is closely related to you.

  21. Thanks again, I will try to do that, but not sure how to find the paternal side.

    Do the number of generations make a difference? Gedmatch says we are separated by 1.7 generations.

    • Gosh, I thought I had a handle on my understanding, but I seem to have confused myself. I do have a cousin match with no x match and we match at 144 cm with the largest at 47 and my niece matches that one with 84.9 with 35.7 at 3.7 generations.

      I think it is from the paternal line, but I have really confused myself. I intend to study this gedmatch info and try to figure it out.

      I can not thank you enough and will continue to follow your blog.

  22. Hi Kitty,

    Here is the info:

    Aunt & Dad
    Half Identical 2858 cM – 44 segments
    Completely Identical 1015 cM – 37 segments

    The possibility I had in mind is
    Aunts Mother = Sally, Aunts Father= Hank
    Dads Mother = Sally, Dads Father = Hanks Father

    Additional relatives who I have 23 & Me data for include:
    Aunts daughter
    My 1/2 sister (share Dad in common)
    My 1/2 sisters daughter & son

    Initially 23 & Me identified my niece as my grand daughter.
    My nephew shares a great deal of both half identical
    And complelty identical DNA with my father (his grandfather)

    Thanks so much for your reply

  23. Hi Kitty,

    Apologies- I didn’t see your reply to my 1st post before adding the 2nd.

    Your answer to my first post took my back to 23 & Me to look at the DNA shared between my father and my 1/2sisters son. the identical DNA shared between them is on X.

    The overall breakdown on their shared DNA is as follows:

    Half Identical 1481 cM – 27 segments
    Identical 53 cM – 2 segments

    When I read your reply about the unlikelihood that they would share any identical DNA I thought that maybe this would be the smoking gun lending possibility to my fathers real father being the man he knew to be his grandfather…. then, I saw the post about x, and uncombined… and I see that maybe it’s not that simple. Any thoughts?

    • A man has only one X otherwise he would be a girl so his X matches are always fully identical, thus that is not meaningful

      As to your puzzle, I am not sure why you think the grandad might be the Dad, those numbers look like normal full siblings to me.

      You could test more cousins related to the grandad

      • Hi Kitty,

        Thanks for the feedback. I created a McGuire Chart plugging in the numbers and was wondering if there is any way I could email it to you? The one hazy area is whether or not the total percent shared for full siblings (via 23 & Me data) is solely the 1/2 identical figure, or, the 1/2 & completely identical added together. I had sent you 2 vinos the other day- hopefully those went thru. 2 more on the way.
        Grateful for your generosity in sharing your knowledge!

  24. Gosh, I thought I had a handle on my understanding, but I seem to have confused myself. I do have a cousin match with no x match and we match at 144 cm with the largest at 47 and my niece matches that one with 84.9 with 35.7 at 3.7 generations.

    I think it is from the paternal line, but I have really confused myself. I intend to study this gedmatch info and try to figure it out.

    I can not thank you enough and will continue to follow your blog.

  25. Ms kitty, have all my questions, I bought you a glass of wine.

    Still trudging forward, but getting cross eyed with numbers.

  26. Hi,

    I have found a cousin on 23andme and our family trees are not connected. My cousin heard rumors that his father’s mother was actually his sister. So Jane and John were raised as siblings, but Jane may have actually been John’s mom. There was no mention of who John’s father could have been. My cousin, James (all names changed), is John’s son.

    Some of my family lived in the same town where Jane was located when she, supposedly, became pregnant with with John. My grandfather and great uncles were near the age of Jane when she got pregnant, 18.

    I ran our 23andme data through the relationship estimator and we are estimated to be 1C1R [11111] or 1C [10110]. My daughter and some cousins on the paternal grandmother side have taken the 23andme test. My mother will be taking the test and another cousin on my paternal grandfather side will take the test too.

    Jame’s DNA Match to me
    Based on Seg of 5 cM or greater
    Total cM 567
    Longest Segment cM 48.2
    # of Segments 21
    % Shared 7.660

    With all the data we have and will have, where can we go to better narrow down the potential relationship possibilities?

    Thank you in advance!

    • One problem with Family Tree DNA is that they include segments smaller than 7cM. After you toss out those smaller segments, if you are still matching for about 500cM then still likely in the first/second cousin range

      Sounds like you are doing the right thing, getting as many family members to test as possible to sort this out. Most important is your mother. Does she have any brothers? If she does not match then it is on your dad’s side.

      Another possibility is for James to get his Y DNA tested which may provide a surname …

  27. I got my results from 23andMe with 1090 cMs, 20 segments, 14.6% shared and says we’re 1st cousins, is that even possible? We are definitely half relatives, if that helps.0

  28. Hi, I could not complete all questions, and I’m not positive of my parents being my actual parents, but my one and only match was with someone I did not know and about 20 yrs younger. Ancestry DNA had put us as 1st cousins at 663 cm & 37 markers? She too is not at all positive of her birth parents. Could she possibly be a half sibling or a half Aunt? Thank you

  29. Thank you so much Kitty! I’m only 2 days new to this and I have read how it works but is so confusing to me, especially having no other DNA with anyone to go by & when I put 35markers, was supposed to be 32. I’m sorry to have had bothered you with this, but I’m just lost…. 🙂
    Thanks so much!

    • Shannon
      Patience … Give yourself some time. Keep reading and looking at your results, it will start to make sense eventually

  30. Hello Miss Kitty,
    More wine coming your way. I’m female and match an unknown man on Ancestry. I’ll call him D.
    •D matches his known half-sister at 1377 (they have the same mother).
    •D matches his own granddaughter at less than 1300.
    •D matches me at 1373 cMs across 44 segments.
    •D’s son matches me at 961 cMs across 25 segments.
    •Ancestry has defined D and me as Close Family –and D’s son and me as 1st Cousin.
    * In the Close Family category, I know D is not a great grandparent or Uncle, nor is he a child of my full sibling.
    * At 1373 cMs, I believe D could possibly be a half-brother or half-nephew.
    * If D is my half-brother, his son is perfect for half-nephew at 961.
    * But if D himself is my half-nephew, then his son’s number is very high for a great half-nephew. What do you think? Thank you so much.

    • Wanda, it sounds like you have answered your own question and eliminated the other possibilities. He is your half brother. It would be good to get him to upload to GEDmatch and I would happily look at the comparison there for the two of you.

  31. Hi Kitty can I call upon your expertise.
    I have a match on ancestory as a 1st cousin, we share 804cms (gedmatch)
    i share 373 cms with his daughter
    he was adopted and only info was that his bio father was a young (my name)
    I have no idea who my fathers father was as he was brought up by his grandmother (young)
    at 1st the result looked as though I am a half Nephew but there is a 3rd person who he has a match with as do I on ancestory who is a relation of my grandmother (young nee bushnel) he comes up as 3rd or 4th cousin
    he hasnt uploaded to gedmatch

    any thoughts?

  32. Kevin –
    That is really not enough information. What are your relative ages? So the issue is that if he is a Young why does he have this 3rd/4th cousin match with your grandmother? Sounds like he is related to your Dad who would have both lines. Did your Dad or you have any brothers?
    Get as many known relatives of yours to test as are willing to help with this mystery.

  33. Sorry Kitty I didnt put it very well.
    I am 62 he is 70
    the 3rd/4th cousin is the relation to me to the 3rd person who is a descendant of my great grandparents.
    my dad has a couple of living cousins as do I so i will see if they can get tested

    Thanks

  34. Basically want to tell what relation he is to me
    this is the gedmatch result

    Chr Start Location End Location Centimorgans (cM) SNPs
    1 238,254,256 240,773,066 7.6 716
    2 77,916,406 133,326,827 42.8 5,861
    2 202,658,096 235,840,151 48.0 5,526
    2 236,089,121 242,565,979 13.4 1,207
    3 120,836,583 151,154,829 32.1 4,311
    3 157,730,821 187,609,004 30.2 3,766
    4 6,829,453 10,337,857 9.8 824
    4 84,460,381 92,046,301 8.4 1,025
    6 6,171,146 21,798,151 27.8 3,191
    6 124,399,036 138,863,401 18.4 2,268
    7 7,972,287 26,162,119 27.7 4,051
    7 145,948,007 152,927,182 15.4 1,356
    8 37,288,402 72,408,012 27.0 3,726
    8 74,856,303 115,097,126 29.3 4,700
    8 139,853,147 146,241,933 10.7 1,143
    11 22,308,958 108,678,237 71.1 11,209
    12 93,073,105 126,075,474 47.1 5,852
    14 52,679,619 99,760,931 64.1 8,221
    15 20,614,243 37,027,402 37.9 3,141
    15 67,910,978 77,127,099 8.4 1,168
    15 93,491,713 98,574,626 14.8 1,241
    16 7,400,811 10,252,326 7.4 849
    16 12,199,639 22,744,262 16.8 1,577
    17 10,164,422 58,988,240 63.1 6,979
    18 102,535 2,881,478 8.4 662
    19 489,994 38,923,549 56.7 4,535
    19 40,112,681 57,932,919 32.2 2,941
    20 7,448,401 13,190,328 13.4 1,290
    22 37,959,275 43,840,446 8.6 1,007
    Largest segment = 71.1 cM
    Total of segments > 7 cM = 798.7 cM
    29 matching segments
    Estimated number of generations to MRCA = 2.1

    435222 SNPs used for this comparison.

    • The data is a very good fit for half uncle. There are other possibilities based on cMs and ages (1st cousin, half first cousin) but the low number of segments suggests a close relationship.
      How large is the match to your grandmother’s line by this 3rd person? Unless his match to you and to the adoptee triangulates these could be from different unrelated lines. For example this 3rd person could be related to your grandmother on one line and to the adoptee on a totally different line.
      Get a few more cousins to test, a cousin on each grandparent’s line and perhaps each great grandparent line also … the more the better!

      Also if you are interested in figuring out who your father’s father was, go to DNAadoption.com and take some classes or just read their materials.

  35. Fantastic post Kitty. Thank you. I have my own situation I was hoping to run past you:

    I have a match on AncestryDNA that is 793 centimorgans shared across 32 DNA segments. Ancestry thinks that this is my first cousin.

    I can identify this person as being from my mother’s father’s side due to ethnicity. My mother was adopted and she never knew her birth parents. It is almost certain that her birth parents never had another child after her.

    Accordingly, I am almost certain that this person cannot be my first cousin.

    I believe this person is my mother’s half-sibling, i.e. my half-uncle. Do you think this is correct? The only other relationship I think could be possible would be first cousin once removed (i.e. my mother’s father’s sibling’s child, i.e. my mother’s cousin). However I looked at the histograms for the latest SharedCM project (August 2017) and this would put us in the 99th percentile for amount of DNA shared, which seems very unlikely.

    Can you tell me if my analysis is correct or if I’m missing anything? I am also a little vague as to the significance of / context for our centimorgans being shared across 32 segments.

    I would be so grateful for any light you can shed on this!

  36. A mother, her brother, her son, her daughter compared to a non-related Male and his Half brother.
    Only the Daughter’s Autosomal test matches the non-related Male. 48.5cm Total and 48.5 largest.
    Is the Daughter alone, apparently related to the otherwise non-related Male from her Mother’s side?
    The individuals do not share matching mtDNA haplogrouping.

    • The daughter would be related to the unrelated male on her father’s side since her mother does not have this match. I removed the kit numbers, we never publish these for privacy but I will take a quick look and email you.

  37. I uploaded my raw DNA to GED MATCH. Not sure why because i have no idea what all this means. are there people you can hire to look at these results . says i have 90 matches. i have like 3 that are highlighted in green. Ughhhhhh ,
    any help would be appreciated.

  38. I have a question about full vs. half siblings. I am an adoptee that has found my bio mom and siblings. My brother and mom both tested at Ancestry and I uploaded both to Gedmatch. My son tested at 23andme and I uploaded to Gedmatch.
    As far as I can tell my brother and I are full siblings. Our mom is from the San Luis Valley. The gedmatch test for “are your parents related read”:

    Mother 4.6
    Brother 2.5
    Sister(me) 2.8
    My son parents not related.

    Our numbers on Ancestry are:
    Brother to sister 2,515 65 seg
    Brother to mom 3,478 49 seg
    Sister to mom 3,458 62 seg

    Our numbers on Gedmatch are:
    Brother to sister 2635.5 145.9 on X. Gen 1.2
    Brother to mom 3586.2. 196.1 on X. Gen 1.0
    Sister to mom 3586.1. 196.1 on X. Gen 1.0
    My son to brother 1815.6 145.9 on X. Gen 1.5
    My son to My mom 2158.8. 174.1 on X. Gen 1.4

  39. Suzanne-
    All those numbers look pretty normal but I am not understanding the “are your parents related?” result – are those generations (gen) or cMs? Does your mother know who your father is? And who her parents are? I will email you

    • Hi Kitty,

      The “are your parents related” result on Gedmatch is given in MRCA form: most recent common ancestor. My mother is 91 and has dementia so I don’t know if she would be able to tell me.

      Thankyou for any guidance you can provide.

      Suzanne

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