Responses
I had read the same things too on the other manga (monshou something I can't remember) they also explain the same reason why they married they own siblings. At that time I'm also felt it's kinda weird coz for me it is impossible to have romantic feelings towards ur siblings (maybe bcoz I always brawled with them I guess)
i knew this was normalized back then but the concept of incest breeding is so weird im glad we made it illegal