Talk:Ken Kaneki/@comment-3173617-20150622023314/@comment-26409128-20150622114139

I think it's similar to age differences. Like people who were 30 and up married 15 year olds. It used to be normal (in the West, too) but now it's not and considered a taboo.

Maybe they marry even more distant relatives than just cousins in the Tsukiyama family. But that wouldn't cause that many genetic defects I suppose. Maybe it's like a inherited disease.