Yesterday brought great news from my cousin SL! She did a 23andMe test a few weeks ago and her test results have come in. I am particularly happy she did the test as I can now map parts of my father’s DNA sample specifically to his mother as cousin SL is a 1st cousin on his mom’s side.
I have another cousin (MS) who is related to me via my father’s mother – but – that cousin is also related to me through my father’s father. So, as a double cousin, I’ve not been able to pinpoint any of her DNA share with my father to one particular side of his family as no one else on my grandmother’s side of the family had tested.
The first thing I did with cousin SL’s DNA results is map out the segments we share. Using Kitty Cooper’s Chromosome Mapping Tool, I updated my father’s map. So now, my father’s chromosome map now has a “maternal” side reflected. Prior to yesterday, all the red parts were not there 
my father’s chromosome map as of Jan 15, 2017
My cousin MS is also a cousin to SL. However, the two of them are not double cousins (to the best of my knowledge), so I next compared their DNA against my father and against each other. In doing this triangulation, I found that of the 11 segments my father shares with his double cousin MS, 5 of them triangulate to his cousin SL. This means I can mark these 5 segments my father and MS share as having come from my great-grandparents William Lawhorn & Pearlie Mae Kilpatrick – common ancestors to all 3 (to my father, MS, and SL).
On top of this, I found that cousin SL shares several segments of DNA with my father’s nephew that she does not share with my father. These segments represent DNA that my uncle inherited from his parents and my father did not; my uncle then passed that DNA down to his son.
I am glad to have this updated chromosome map for my father, for as I get more matches in the future, if they have a segment that triangulates to my father and one of these cousins, I will able to pinpoint which part of my family tree to focus on as we seek connections.
So many intricacies to figure out for sure!
