The reality that if a child is conceived it could resemble something that looks like a character " From the hills have eyes". Of course, that's not always the case. Rumours that serial killer Ted Bundy's grandfather was also his father because he had sex with Bundy's mother. But we all know it didn't turn out well for him but it weren't his appearance that was the problem.

Saying that, we must be all inbred if you think about it.