Keeping it in the family for a single generation is not a big deal across an entire bloodline if your little sister is absolutely perfect. You shouldn't let your kids / grand kids / great-grand kids do it themselves. A four generation gap between sisterfuckers is probably fine. Certainly, it isn't nearly as disastrous as racemixing.
>>714439179
You'd do it too if your brother was Andrew and you had their parents
It's literally the most standard case of shared-trauma bonding in media
>>280188367 >>280188785
This has been the best thing to happen in incest media in fucking decades.
Especially how realistic it is in portraying a BPDemon like Ashley and an abusive-doormat like Andrew
Repeated incest over multiple generations creates jews/muslims/indians, which are truly horrible. A single generation is fairly safe if you can't a better partner than your sibling, mind you. Certainly not as gross as burning coal.