LGBTAitP #31: Cuddles Are On Back Order. Have Some Snuggles!

[pffh]

*skimming Wiki*
People have also looked at things like the Israeli kibbutzim for the Westermarck effect, though. I know I've heard of that before. So having the children be siblings isn't necessarily necessary, just raising them together from early childhood.

Yeah I've read about this too. A related thingy is that while people that are raised together aren't attracted to each other, siblings (and parents/children) that have no contact until adulthood are more likely to be attracted to each other than not.