A DNA Question

Question

Have a person whose paper tree and my paper tree say we are related, 4th cousins once removed. But we don't have a DNA match that shows up on Ancestry. Is it possible to still be cousins and not have any DNA that matches at that distance? Or does this mean that one of our trees is in error?

Answer 1

Have a look at the Cousin Statistics page at the ISOGG Wiki. In short; yes - there's a 52% probability you won't share significant DNA with a fourth cousin once removed.

You could upload your DNA to Gedmatch and have them do the same, so you can compare in detail directly. However, I think Ancestry includes pretty low cM matches so I wouldn't be too confident you'd find anything different that way.

Comments

Thanks for posting the article-very useful.  I'd been wondering how reasonably distant the companies could find matches.

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No problem. Obviously in this case, they look at the average. In some specific cases, a close cousin will share less DNA than expected, but in others, they will share more (I have found valid matches with cousins as far as 8C1R and 9C, though those are rare).

Answer 2

Yes. You don't need to have a DNA test to confirm you are related. For example, I found out I was 3rd cousins with someone long before I did a DNA test. She did show up in the results, though when I had mine done.

Paper trails and DNA tests work hand and hand and cement the bonds.

Answer 3

In addition to the other answers... its also possible that there was an NPE (non paternal event?) somewhere, meaning that one of you may actually not be biologically related.

But that can't necessarily be proven, just because you don't match.

Answer 4

This is where having your siblings, parents and first cousins DNA test will help you.  You may not share a DNA match but one of them might.