Interpreting Degree of Relation from multiple DNA Matches.

[M_ONeill]

Hello, all.

I've recently been asked to go through my paternal 1st cousin's DNA matches to see if I can find anything interesting. I've found an interesting cluster of results and wanted to get a collective opinion on whether getting a ballpark estimate on the degree of relationship was possible. The family in question likes to keep their tree mostly private, so I hope you'll excuse me skirting around the names.

So, my cousin has five matches from separate Ancestry kits, all descended from one man (we'll call him 'A'). These five results all descend from three of A's Children (A1, A2, A3):

A1: Two results, grandchildren of A, children of A1. Male and female in their 60s (31 and 32cM shared with my cousin respectively).

A2: Two results, a male grandchild of A and child of A2 (11cM shared), along with his own son, the great-grandchild of A (10cM).

A3: One result, a female descendant of A (8cM) Unsure whether this is a grandchild, great grandchild, etc, but she is definitely a descendant of A through A3.

There is also a sixth result, a person of unknown gender (13cM). This person descends from a woman of the same (maiden) surname as A, from the same area (We'll call this woman B). A number of Ancestry trees place her as the older sister of A from the same parents, and conversations with the descendants of A suggest that this link is most likely correct.

Now, I'm aware that these are all very distant relations, but can anyone give an idea of what sort of degree of relationship we're looking at here? There is a shared surname in this branch with our own tree, and some evidence suggests that A's family left Ireland (where mine and my cousin's ancestry remained based) in the early 1800s, with A and B's own father being born in Canada. Also, is there any potential significance in A1s children having a higher cM match with my cousin or is that just 'the luck of the draw' in genetics terms?

Thanks in advance!   

[Petros]

For the same level of relationship the cM matches seem to vary considerably. I have 15 confirmed descedants of one GGF who range from 10 to 95 cM.
But the closest match is a 3C1R not one of the 3Cs!

3C 50, 58 and 86 cM
3C1R 14 to 95 cM
3C2R 10 to 35 cM

I'd suggest that your results are consistent with the connection to your cousin being a 3C1R

[M_ONeill]

Thanks for the response, Petros!

I have to say, I'd be surprised if the link was that close - but that's with me assuming the link is through the name/line that I suspect it is. It is of course possible that the connection comes via an unknown or undiscovered family link marrying in through one of the later generations - or at least later than their initial ancestor's emigration from Ireland.

I'm also entertaining the possibility that the higher matched DNA from the descendants of A1 may be due to us sharing more than one related line of ancestry. This is currently just a theory based on some shared surnames and locations in *other* matches. Need more research on that front.

Also, I've finally done my own DNA test, which might hopefully give some extra detail!

[brigidmac]

Do you know if any of the siblings are twins or if any Married a cousin from same line

Both situations  can increase amounts of cm in shred mathes

[hurworth]

People related on just one segment can be from quite far back.  It's likely that all of these matches are triangulating with your cousin on the same single segments, and that A, their ancestor, had they tested would have shared around 32cM (the greatest amount your cousin shares with any of them).

Has your cousin uploaded their DNA anywhere else?  Some members of this family could be at other sites and this could help to narrow down how far back the relationship is.

[M_ONeill]

Thanks for the responses, all!

Well, I just got my own DNA results back in the past few days: While I don't match with as many of this family as my cousin does, I match with enough of them to fully confirm that our families are linked. I got matched with descendants of A, A's aunt and even another brother of A that my cousin doesn't match with.

I don't think any of them are uploaded on GED match, or any other websites, sadly, so I can't get a more specific look at where we match. I've got some matches that come from specific areas of Ireland that have turned out to be shared matches with some of A's relatives, so I'm hoping that digging in there might uncover some links!

[Ruskie]

https://dnapainter.com/tools/sharedcmv4

[Biggles50]

For 32cM, DNA Painter reports

53% Probability
5C3R † 6C 6C1R 5C 6C2R 4C1R 5C1R 7C Half 3C2R 4C2R 5C2R 7C1R 3C3R 4C3R 8C or more distant

So quite a wide range is possible

[4b2]

I don't pay a huge amount of attention to cM, as every cM value can be the generation before or after the most likely one. My focus is on finding clusters of matches that triangulate marriages.

As an example, I have one half 2nd cousin match, who overlaps with two clusters of matches - Evans and Bebb. And then the Evans cluster overlaps with another smaller one for Humphreys.

Are you able to find DNA matches that triangulate any marriages?

Regarding the matches that you mention, are any of them shared matches with each other? The smaller ones may not be.

But the cM you mention in the ranges are consistent with those degrees of relation. If your cousin can get other close relatives tested, it will narrow the window or relationships.

You also have to consider the nature of half matches.

Yesterday I researched the tree of a 75cM match on MyHeritage. The degree of relation is most likely giving us an descent from a woman born in 1850, but I can't find any matches that correlate with her husband. So, I think it's probably more likely I am a descendant of one of her siblings, or a child born out of wedlock; and that we just happen to be at the very high end of cM that can be inherited.