Icy brings some philosophy to the topic of ancestry.
The Tree of Life
We're always proud to find an interesting ancestor, especially one way back long ago, but few acknowledge just how many ancestors we had. For instance, my great great great great grandfather was Lord Mayor of Portsmouth, but I prefer to phrase it that way. I wouldn't say the more accurate "one of my thirty-two great great great great grandfathers was so-and-so, or, in this age of gender equality, "one of my 64 great great great great grandparents..."
Of course, I probably didn't have 32 great x 4 grandfathers. If things went that way, then my great x 32 grandfathers would have colonised the earth, even by today's high population numbers (I'd have around 8.6 billion of them). No, our population implosion is carefully controlled by inbreeding. If siblings marry, then their offspring's grandparents are duplicated. If two cousins marry, then theirs have a duplicate great grandfather and great grandmother. Going further back, it becomes far more likely that our second, third and fourth cousins may have married – they may not have even known they were related.
Yet it's somehow awkward to uncover any inbreeding in our family trees. Leaving aside questions of social acceptability, the fact is that trees don't grow like that. They have trunks which divide into boughs, branches and twigs. At the end of each, we are the little green leaf that flutters. Our accurate family tree would have some branches which ended not in a twig, but which turned back into another branch or bough. The whole thing would resemble a Henry Moore sculpture. Oh, and there would be only one tree. It's very large and messy, and we all grow upon it. And it's not just us, but Darwin's apes, other mammals, fish, dinosaurs, plankton, plants and whatever seeded life in the first place.