octuple-third-cousin
A living being who has nothing but sixteen great-great-grandparents in common with someone else. Zero parents. Zero grandparents. Zero great-grandparents. Just a bunch of old people.
My dog is related to my cousin’s dog. They’re octuple-third-cousins. I don’t know why.
That kid at school is an octuple-third-cousin. He’s related but not cool.
My mom’s octuple-third-cousin showed up. He had no idea who I was.