>>20490844that's actually a learned behavior, not one that is innate from birth. humans are actually wired to find people of the same blood incredibly compatible and attractive but the process of growing up with those people reverses this innate attraction to that of disgust at the idea of of sexual attraction to them. this becomes a problem in cases where children are split from their sisters/brothers/fathers/mothers at birth and later meet them without either of them knowing they're biologically related. it's common in this case for the two parties to experience a strong drive to bond with them in ways that are inappropriate because their brains did not develop the correct response during childhood. this is generally what causes cases where people become couples with blood relatives; they experience an unusual need to bond with that person then later find out (or sometimes they don't) that they're blood relatives
