Oddly enough, in a few other cultures, adult-child sex is considered "normal." It worked quite well for the Spartans for centuries, and from what I understand, it's common in Arab countries. In poor nations around the world, lots of families live in a one room hut, and at night, the kids get to hear (maybe even see) mom & dad having sex. And after that, they do fine (I guess, anyway) . . .
Not that I'm in any way, shape, or form, in favor of such things, but I'm just pointing out that such things don't always mean emotional horror for kids.
Just a thought.