We have the Clark/Nelson Family Reunion every year. People bring their significant others. Anyone I don't immediately recognize, I introduce myself and talk to them. They are either family or a significant other. I just cannot imagine getting horny if I find out we are actually related. Unless 23andMe is reporting 0% DNA--I don't fuq thru the family.
I do remember when I was 17, my friend ended up dating and then quickly sleeping with one of the hottest girls in our school. She confided in him that some of her male cousins have had sex with her. He said it didn't seem like it was against her will, but he didn't dig deep enough to discover if it was 1st/2nd/3rd cousins but he was repulsed by it--as was I. I think they dated 2-3 months before things ended.