I rarely complain about voting, but it annoys the fuck out of me that this question is in the negative. It’s actually a damn good question, if poorly phrased.

But it’s true. Inbreeding takes generations to cause significant troubles if there’s no really nasty genetic diseases present already.

Even siblings aren’t going to crank out two headed monsters if they’re the first in the family to keep it in the family. And, once you’re past first cousins, the risks get even lower. Not non existent, just not anything to worry about in the first generation. Again, that’s unless there’s a known issue.