Finding cousins who can help solve genealogical mysteries are what many of us are hoping for when we do DNA testing. The various One-to-Many tools at GEDmatch Genesis list all the people who match the DNA kit you specify. These are cousins or even closer relatives.
The new beta version of the One-to-Many tool is found under the heading DNA Applications in the right hand column of your home page.
My red arrow points to it in the image to the left. It is a much improved tool, more like what was available on GEDmatch. When you click on it, you get a form as shown below which only needs the kit number added.
If you have set up some tag groups (click here for my GEDmatch tag group article), check the tag group box named “All” (shown with my red arrow above). Below is what my One-To-Many result looks like with my tag groups. The kit number is shown with the color of the group it belongs to. Note that when I have a person in more than one tag group, I get duplicate lines for them, one for each color coded tag group they are a member of:
One of the great features of this tool is that every column is searchable by putting text in the box above the column and then clicking the enter key. [UPDATE: this is a Tier 1 feature only and is more directly called a filter]. Another one is sortability via the up and down arrows at the top of the column. When working with my Jewish side, I sort by largest segment to get my closest cousins at the top. The reason I do that is that endogamous populations will often share many small segments from way back so the total cM make a triple 5th cousin look like a 2nd or 3rd ; however close cousins will always share larger segments.
This beta One-To-Many tool includes many of the features GEDmatch users are used to: the link to a tree*, the display of haplogroups, the estimation of generations difference, and the X matching. It also includes the new overlap number which lets you know how many SNPs are tested in common between the two kits. The overlap issue was discussed in my previous article about GENESIS
You can click on any kit number to get a One-To-Many for that kit or click on the underlined largest segment number to compare the cMs of the two kits for either autosomal or X. In both cases you are taken to a prefilled in form on which you can make changes to (don’t yet) before you click the Submit or Search button. On the X comparison, I recommend you click the “Prevent Hard Breaks ” because there is a large gap in the middle for many tests otherwise.
Here is a table with an explanation for all of the One-To-Many column headings:
|Select||The select box lets Tier 1 (paid) members select multiple kits for further analysis|
|Kit||The kit number, clickable to go to the One-To-Many for that kit. Ancestry Kits starting with 2 letters have been uploaded to GENESIS while kits with one letter were migrated and the kit letter tells whcih company: A, 23andMe with M, Family Tree DNA with T, MyHeritage with H, and others with a Z|
|Name||the name or pseudonym of the person|
|email address to use for contact|
|GED wikitree||When GED or wiki appear in this column, click that word to get to a tree for this kit (*currently the Wikitree links are gone, coming soon …) – click here for my post on GEDCOMs at GEDmatch.|
|Age||How many days since the kit was uploaded. Newer kits have this number and the name highlighted in green.|
|Type||This is probably meant to show which chip version but all are a 2 at the moment.|
|Sex||If the user did not put it in you see a U, else F or M|
|Haplogroup||there is a column for the mtDNA haplogroup and the Y haplogroup, self reported.|
|Total cM||The total of all shared segments of 5 centimorgans (cM) or larger.|
|Largest||The largest shared segment with this match. For endogamous groups I recommend sorting by this column (the blue arrow at top). Click to get to the one-to-one autosomal report|
|Gen||Subtract one to get the cousin level. So 4 means a 3rd cousin. A nephew or uncle will be 1.5|
|Details||Click the X to get the one-to-one X report.|
|Total cM||Total matching cMs on the X.|
|Largest||Largest segment on the X, as X can reach very far back in time so only look at the large matches initially. Click to get to the one-to-one X report|
|Source||The testing company or the words Migration – chip version – code letter when it is a kit migrated from GEDmatch. The code letters are A for Ancestry, etc (as explained above under kit number)|
|Overlap||The overlap column indicates how many SNPs the kits being compared have in common. It is color coded to show whether there are enough of them for it to be a good comparison; the redder it is, the worse it is.|
The following is a repeat from a previous post of mine: “In the generation listing your parent or child is 1, an aunt or niece is about 1.5, a grandparent is 2, for cousins subtract one from the number so if it shows generations of 4, the suggestion is 3rd cousin. My recommendation is to follow up with anyone who is 4.5 or less. Start with the closer ones. Accuracy in autosomal matching declines after 3rd cousins.”
It is best to use the DNApainter calculator to figure out the likely relationships. It is based on Blaine Bettinger’s charts plus Leah Larkin and Andrew Millard’s probability calculations: https://dnapainter.com/tools/sharedcmv4
When you find a new DNA relative in your One-To-Many, it is time to use the tool called “People who match both, or 1 of 2 kits,” perhaps a confusing name. What this tool does is list all the kits that are in common with two specific kits as well as the not in common kits. After showing the kits in common, it lists the kits that only match the first kit and then the kits that only match the second kit. There is a form to set the thresholds. Like most tools, start by using the defaults then perhaps move down to 8 cM in common for a less intermarried group or to a higher number for an endogamous group. By looking at the output from this tool, you can often see where this new relative fits into your family.