Would you guys consider it gross to sleep with a cousin?
I mean people just a few decades back were marrying and having kids with their cousin, then in the US it suddenly became illegal and socially unacceptable.
eeeewww.
A few decades back women were still frequently sold into marriage, just to put things in perspective
I think it depends a lot on culture and how close families are, as far as I know in the US families are more isolated from their cousins/aunts/uncles, so it becomes more likely, here in Latinamerica families are extremely close, to the point I see my cousins as brothers and sisters, I grew up with them, so it just makes me feel "eeww" the thought of anything with them.
In reality, incest is not a 100% ticket to birth defects, and it can actually lead to extremely brilliant individuals, probability is still considerable between siblings, but with first cousins the chances are very, very minimal. I'm not sure it should be illegal, but people being grossed out by it is nothing surprising.