And, in Alex’s ending, he marries and impregnates his second cousin and step-sister, Patricia.

How can someone be your second cousin and also your step-sister?

That’s when your dad marries your mom’s sibling’s daughter.

Roll tide.

That would be first cousin and step sister, actually. A second cousin and step sister would be your dad marrying your mom’s cousin’s daughter.

I could never keep any of that stuff straight so I’ll defer to this confident-sounding reply.

First cousins share a grandparent.

Second cousins share a great grandparent.

Third cousins share a great, great grandparent, and so on.

Nth cousin = greats + 1.

Shouldn’t it be

Nth cousin = greats * (n -1)