That's why incest is illegal - and that's why 'village idiots' exist. Firstly if you mate with someone with genes that are too similar, their immune system is weak and they are more likely to have birth defects from brain damage to physical distortions. Swiss scientist Dr Claus Wedekind discovered that women who are on the Pill get reversed preferences. They are automatically drawn to genes that resemble their own. The Pill simulates pregnancy and during pregnancy women are drawn to similar genes because these are most likely to be family members.
Family members are more likely to take an interest in seeing the offspring survive.
Why is it that regular chain stores can't make sexy winter nightwear for women. I'd like some chain store to come out with warm winter bedwear that falls somewhere between Ann Summers and fluffy bunnies.