Example of Double First Cousins who Married Sisters

In one of the Facebook Groups I belong to, a member was reporting how her and her sister married Double 1st cousins. She shared this as a bit of a conversation starter and I just had to draw it out, so I could share with my DNA buddy in my Genealogical Society.

Kathryn wrote: "This is a match to my daughter and my son. I manage all 3 kits. If I was looking at this without knowing the relationship I would probably be asking my husband some questions - as my first guess would probably be half sibling to my children. However, this is my nephew. My sister and I married cousins, their parents are siblings that married siblings. So a brother and sister married a brother and sister and their respective sons' married sisters. Still with me? So this man is a first cousin to my children and also a first cousin once removed twice over - which then equates to roughly the same DNA as a half-sibling.

While this is an incredibly rare occurrence I would think, it does demonstrate that sometimes the obvious isn't always the correct answer :) Especially when looking at relationships in endogenous societies - usually much further back than this bunch of millennial's."

Now a correction to what Kathryn wrote, her nephew and her children are actually Double 2nd cousins, not first cousin's once removed twice over. They are at the same level from all their common ancestors and thus there would be no removed between them. Confusing, I know.

Anyway, enjoy the picture I created to give me and other's a visual of this complicated relationships.