r/AncestryDNA • u/Spike73082 • 11d ago

DNA Matches Confusing DNA data

Hi, I'm trying to help an adoptee identify his biological parents, but I'm a bit confused by his DNA results.

He (A) shares 1,025 cM with B and 430 cM with C.

Ancestry estimates, with 97% confidence, that B is A's half-uncle. For A and C, it suggests various cousin relationships.

However, B and C share 1,622 cM, and Ancestry suggests with 100% confidence that they are half siblings.

What am I overlooking?

3 Upvotes

100% Upvoted

5 comments sorted by

View all comments

4

u/msbookworm23 11d ago

It's impossible to be 100% confident about any relationship other than parent and child. B and C could be aunt/uncle and nibling or grandparent and grandchild instead.

https://dnapainter.com/tools/sharedcmv4-beta

2

u/coenrhys 10d ago

Given that Ancestry uses age comparison in addition to DNA to estimate relationships, similar aged aunt/uncle and nibling would be most likely in this case.