Hello all,

I have not been very active with autosomal DNA the past few months, not because I don't think it is important but more because I've been focusing on more traditional research and there are only so many hours in the day! However, something came up this week with a match and I want to make sure I still remember all this correctly.

The situation is my father (person A) had a pretty high match on gedmatch with someone (person B), and when I ran the comparison they had a 42cM match on #21 with a few smaller matches elsewhere. I ran the "find other people who match" report, and they both matched a third person (person C) on pretty much the same area and length of #21. It ends up that B is adopted and does not have much info on her past, so the assumption is if we can figure out how A and C are related then there is a good chance that this is how B fits in. Unfortunately, there aren't any obvious links to A and C by either surnames or geography.

My question is am I correct that 3 people matching on over 40cM on the same area means it is highly likely they have a common ancestor, and not necessarily that many generations back? I do seem to recall that some areas of some chromosomes tended to match lots of folks randomly, so I'm not sure if that is the case here.

A side question is am I correct about using this to find how the adopted person fits in?

Later,

David McCorkle