I don't see the appeal from the inbreeding standpoint, but I do get it from the "forbidden love" angle. I enjoy myself a good story about secret relationships and the burdens that go along with that.
That's always more of an end game problem isn't it? You're having fun when everywhere you go is somewhere new with something novel, but then you gotta start backtracking for all the stuff you missed. For me though I don't really mind that. If I'm in the mood for a really big sandbox game I'm...