How to confirm a person by DNA with only one decendant?

Question

My paternal grandfathers mother I want to make confirmed by DNA. I have tested her brothers daughter and there is a clear match between my grandfather and his cousin. No doubt that there is a match and a correct conclution there. Both are tested by FamilyFinder at FTDNA.

Answer 1

So your paternal grandfather and his first cousin have both tested and the resukt is as expected. Since the relationship is 3rd cousin or closer that is enough to confirm. So you can confirm your grandfather being a child of his mother and his mother being a child of her parents (the Most Recent Common Ancestors). The same goes for the cousin's side of the family.

See the DNA confirmation help page

Tim