Need advice from Adoption Angels and/or DNA project

Question

I have a co-worker who was contacted by a gentleman who DNA test results calculate is her grandson (both tests were done through 23 and Me).  We know with absolute certainty the relationship isn't grandson, but given family history there is a very high chance this gentlemen is her half-brother.  He was adopted out of Omaha, Nebraska in the 1960s and he does not know for certain who his biological parents were. He may have a lead on who his mother was but has yet to locate her if she is still alive.

Can anyone give me some ideas how they might go about proving the relationship?  My co-worker tells me there are not any living direct male relatives to test and the suspected father is deceased. Those who have been DNA tested are females.

Answer 1

A Aunt/Uncle and a half sibling can show up with the same centimorgans as a grandparent. Also higher centimorgans can result from having more than one dna connection. For instance some of my 3rd, 4th and 5th cousins show up as 1st-2nd cousins because we share multiple connections in dna. Does she have any Siblings that she could test to see where they fall? This would eliminate a sibling of hers being a parent and might confirm the theory that this is a half sibling. Also if she has done any dna painting on her own dna and can tell if some of her dna maternal or paternal she may can see where he matches on a maternaly or paternaly on a chromosome browser. Also if she knows her matches are maternal or paternal she can compare their mutual matches to see if she matches to both maternal and paternal matches or just one or the other. One or the other I would lean toward him being a half sibling if matching both I would Lean toward a Nephew.

All in all I think the best step is to see if any of her Siblings if any will take a test.

Also if he hasn't  already he needs to try to gather his non identifying information and any other documents that Nebraska can give him. Nebraska is a partial info with restrictions meaning: Access for Adult Adoptees born during certain years, and with limits.

I hope some of this may help. Dna is so tricky.

Comments

Thank you! All the responses are very helpful! My co-worker and most of her family are really excited about this, I'm just worried both sides are going to find "evidence" where there really is none just to prove an outcome they want.

She has sisters who may have been tested already, trick will be to either get everyone over to GEDmatch, or to have the others retest with 23 and Me.

I think he is working on getting his records, seems he was born in Denver but adopted out of Omaha. I'm thinking he probably needs to make inquiries in both States.

---

If people are unwilling to upload to GEDmatch you can also try FTDNA and MyHeritage both of which allow uploads and have basic chromosome browser functionality but are more restrictive with information.

---

Does she have any known 1st or 2nd cousins who have DNA tested? By checking whether they share DNA with the gentleman that could indicate which side of her family the match is with.

Tim

Answer 2

You might pay close attention to potential x-Chromosome matches. This man received all of his x-DNA from his mother, a fact that can be valuable when identifying relationships. Half-brothers and -sisters with different (and unrelated) mothers should share no x-DNA. It may not prove of a relationship, but can eliminate certain possibilities.

Comments

Thank you! I never thought about this taking this approach to narrowing the possibilities.

---

The X chromosome does not always recombine like other chromosomes (with a person getting all of one rather than a mixture of two) so occasionally people who you would expect to share X material don't. So sharing X material implies a female line connection, but lack of material isn't absolutely conclusive. If one person has siblings that could also test that might help the odds depending on the exact relationship.

Tim

Answer 3

What are the shared cm's? You can find that by going to DNA Comparison view on the DNA Relatives page and then selecting both of them. Once you have the cm's, go to https://dnapainter.com/tools/sharedcmv4 and enter the shared cm's. It will narrow down the match possibilities. Especially when you consider each of the relatives that have tested. You don't really have to worry about male relatives, autosomal will pull shared matches from both sides of the family.

Comments

Thank you for the link!