Shared Match Relationships

Setup: Whenever I add a Match to my Tree (usually a ThruLines hint, that I agree with), I then check the Shared Matches, sorted by ProTools by the closest relationships.  I first scroll down the list to confirm that, indeed, several of them have the same MRCA (the first thing in the Notes field). I then usually look at each one (usually down to 100cM) to see if I can link them to the base Match and/or place them in my Tree and add them to my . Usually this is done at AncestryDNA, but sometimes at MyHeritage.

Topic: In my spreadsheet I have a column for the relationship to one of the closest Matches. Format: 209cM/1C2R: Match Name.  This is strong, additional, evidence that this branch of my Tree is “fluffing out” correctly. Some observations about this relationship:

1. Usually the relationship is exactly right.

2. Usually AncestryDNA offers two alternative relationships. One is a “full” relationship, like 1C2R; and the other is a “half” relationship, like half great granduncle. These are equivalent from a DNA (cM) “math” standpoint – they would have the same cMs on average – the DNA alone couldn’t tell the difference. But relatively few of your Matches will be “half” (indicating their MRCA is one person with two different mates). You can usually tell them apart by how they fit in your Tree, or by their ages, or by a consensus among their own shared Matches. Bottom line – it’s usually the full relationship.

3. However… in a few cases the relationship doesn’t mesh with where I think they go in my Tree. There usually are other equivalent relationships; and a simple click on the Shared Matches estimate at AncestryDNA will quickly bring up a list. In this case, 2C1R, was on the list and that agreed with the genealogy.  An alternative is to keep the DNA Painter Shared cM Project tool handy – just type in the cM amount to see the equivalent relationship and other relationships that are found almost as frequently.

4. If I cannot find a reasonable close relationship, I force myself to dig a little deeper… Sometimes a Match’s Tree skips a generation or adds an extra one; infrequenly the Match has shifted the test taker to a parent or grandparent (the test taker appears to be the child of someone born in 1880…). There are several ThruLines Trees that “skip” a generation in order to generation a Match within 6C range. Sometimes, I can figure it out and put the “corrected” version in my Tree; other times I just set it aside, and NOT include that line in my linked Tree, and highlight it as probable wrong in my spreadsheet and in the Match Notes (so I don’t stumble over it again).

Bottom line: with larger Shared Matches than 100cM (or so – use your judgment), the AncestryDNA relationships are pretty accurate; but occasionally we need to use one of the other, equivalent, relationships. This relationship is a pretty good Quality Control check.

[22DK] Segment-ology: Pro Tools 27 – Shared Match Relationships; by Jim Bartlett 20260327