I find the whole incest porn thing kinda fascinating. I'm not into it myself, but I'm surprised how popular it is.

One thing I think is interesting is that, in a way, it's the last taboo that isn't straight-up rape or nonconsensual shit. Other fetishes that used to be way outside the mainstream, (stuff like bondage, masochism, cuck play, you name it) now have popular reddit subs and show up in the kinds of magazines you find at the supermarket. Incest is sort of the one thing that still makes kinky, sex-positive people turn green.

Edit: And no, I don't care whether you think I'm into incest porn or not. Also, the "step-bro" meme will never stop being funny to me.