DNA & A Question of Paternity: Part 2 – Starting with what we knew

Last week, I introduced a project I have been working on to try to use DNA to learn about the paternal ancestry of someone who wasn’t sure of their father’s identity. As I mentioned before, I won’t use any real names here; I’ll call the person testing “Bob.”

We ordered tests, sent in saliva, waited, and got back results. And as many people with unknown parentage might experience, there were no half sibling or parent/child matches to instantly solve the puzzle. Ethnicity estimates did not yield any particularly enlightening information (there was no indication of 50% of Bob’s DNA reflecting ancestry from a different continent than expected, for example). There were some relatives in the 2ndor 3rdcousin range, though, so I certainly had something to work with.

Before digging in and trying to build trees for all of these matches and figure out how they fit together, I took a step back to think about what we already knew. I started by looking at Bob’s family tree according to the paper records (ignoring DNA for the moment). Even though we were fairly sure that the mother Bob grew up with was his biological mother, and that the father he grew up (his legal father) with probably was not his biological father, I didn’t want to take anything for granted. (Neither Bob’s mother nor his legal father were available for DNA testing to test these assumptions more directly.)

By building out Bob’s maternal and “paternal” family trees, I could test the assumptions that Bob’s mother was his biological mother while his father was not his biological father. More specifically:

  • The tree for Bob’s legal father: I expected no DNA matches to have these ancestors in common with Bob. If matches appeared on this side, I would have to explain why – a match with his legal father’s ancestors could match through another side as well; Bob’s legal father may have been related to his biological father; or maybe Bob’s legal father actually was his biological father after all.
  • The tree for Bob’s mother: I expected at least some DNA matches to have ancestors in common with Bob on his mother’s side. There is no guarantee of maternal-side matches appearing, but it seemed likely there would be at least some (eventually). If not, I would have to reexamine that assumption, too.
  • The GEDmatch tool “Are your parents related?” stated that there was no indication that Bob’s parents were related, so going back at least a few generations, the genetically maternal and paternal branches should be distinct.

Using some family notes, obituaries, online vital records, censuses, and more, I built Bob’s tree, including about four generations on his “father”’s side and about five generations on his mother’s side. While this tree wasn’t built to Genealogical Proof Standard, I tried to be judicious about the individuals I added to the tree (I might use an online tree to suggest a possible link, but I would only add the link myself where I found at least some documentation to back it up). Some errors could still be present, of course.

In addition to finding names of ancestors, I also made note of where these ancestors came from. Bob’s legal father’s ancestors were mostly from the Northern United States and Ireland; his mother’s ancestors were mostly from the Northern United States, and knowing these locations would prove helpful. Next step, trees for Bob’s DNA matches…


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