>>3274576Actually, this isn't as rare as one might think. People are naturally more attracted to those with similar genetic 'components.' We are more attracted to similar genetics because of our natural drive to pass on our own genetics to the next generation. This is also why being racist as fuck is totally normal and natural, and anti-racism isn't.
There's a phenomenon called the Westermark Effect (
https://en.wikipedia.org/wiki/Westermarck_effect) where you become not attracted to anyone you grew up with until age 8 or so. Sometimes brothers and sisters are separated at birth, and they meet later on without knowing they are brother and sister. If you are one of these people, you will feel uncontrollable attraction to your sibling since you are so similar genetically. This is much different than what's being portrayed in the OP's image.
But incest is taboo for good reason. We have this aversion because the Westermark Effect is so strong.