Monday, January 15, 2018

Desperately seeking Susan: Part 6

(Continued from Part 5)

Within a year of starting her DNA search for her biological family, Bonnie* matched two maternal aunts Bridget* (Part 3) and Grace* (Part 4), and her birth father (Part 5), and identified her birth mother Gail* (Part 5). She has now reunited with both birth parents in person.

In JANUARY 2018 Gail received her AncestryDNA results, confirming their parent/child relationship.

Gail in Bonnie's match list – DNA confirmation

Gail also matched Grace as expected, and asked for my help understanding what their match means.

Gail in Grace's match list – note her Italian ethnicity

In Part 4 Bonnie's search inadvertently revealed that her birth mother was a subject of misattributed paternity, also referred to as a non-paternity event (NPE). My working hypothesis was that Bonnie was the daughter of Grace’s paternal half-sister, who was unknown to Grace. (Incidentally, there was also a recent NPE on Bonnie's paternal side. Even if we could have identified the ancestors of her highest paternal match at 23andMe, a second cousin, it would not have led us to her birth father.)

Possible relationships for matches in AncestryDNA's CLOSE FAMILY – 1st COUSIN category include half-sibling, full aunt/uncle, full niece/nephew, grandparent/grandchild, and double first cousins sharing all four grandparents.

AncestryDNA does not list the half-sibling possibility under actual DNA results

People with any of these relationships share on average 25% of their DNA, and it is not obvious from shared autosomal DNA amounts alone which relationship is the correct one, so we also need to make use of any other information available, such as:

– We can exclude relationships that are not possible based on circumstantial evidence (ages and other tree data).
– We can analyze shared X-DNA at GEDmatch to check whether possible paternal half-sisters satisfy the requirement that they share their father's full X chromosome.
– We can analyze shared autosomal DNA at GEDmatch to check whether matches share fully identical segments, which double first cousins sharing paternal and maternal grandparents are expected to share.

Grace and Gail were born in the same area only four years apart and neither has any full siblings to my knowledge, so we can exclude the grandparent/grandchild and full aunt/niece possibilities. They have unrelated known mothers and don't share fully identical segments (established by a one to one autosomal comparison with graphics at GEDmatch), so we can also exclude the double first cousin possibility.

Gail and Grace share their father's X chromosome

A one to one X-DNA comparison at GEDmatch confirmed they share a full X chromosome, consistent with my working hypothesis and the only remaining possible relationship for their DNA match, paternal half-sisters. Furthermore, their shared matches belong to the tree of Grace's known father Carlo* Jr, indicating that they are both his biological daughters.

Gail's biological father was not the person she thought it was, and none of her parents are alive to ask about it. It is a hard pill to swallow. I can explain what the DNA is saying, but any new information revealed must ultimately be processed emotionally by those affected in their own time.

*This is a true story. I have permission to blog about the people who asked me for help but have not used their real names for the sake of their privacy. I have tried to limit my writing here to information pertinent to their DNA searches, but have shared other details I found with them in tree format.

{Related resources can be accessed via ISOGG's Wiki page on DNA testing for adoptees.}