To be able to know that, we would also have to know what the consensus would be on sibling incest under communism.>>4860
Recently it occured to me that perhaps it's so prevalent in Japanese otaku media not only because of what >>4865
said, but also because so many Japanese youth are an only child. They didn't really get to know what having a sibling is like, and if the Westermarck effect is a real thing, that's why they consider sibling incest a relationship like any other where romance can flourish, although a taboo kind of relationship. The taboo of it turns it into a fetish, a mere sexual fantasy for Japanese otaku who either never had a "sibling figure" in their lives or are so alienated that they don't care for certain social norms and proudly (but secretly) accept their taboo fetish despite having a sibling themselves. Sometimes it's partly because they have a brother or sister that they grew up with, but their family is a bit fucked up emotionally (in this case, this can happen between other family members). Obviously the prevalence of the fetish itself in the media they consume helps.