I once fell into bed with my sister’s husband’s sister after a family wedding. We weren’t related at all, in the consanguinity (blood) sense. But we thought it was amusing that we might be brother-in-law and sister-in-law, and committing some sort of sex crime.
We looked it up later and discovered that we weren’t. We were mildly disappointed about that.
But real incest strikes me as worth avoiding. I fancied my aunt, my mother’s youngest sister, for a while when I was about nine or so, and she must have been in her mid-twenties. I remember I planted a more than family kiss on her that Christmas. She pretended to be impressed, which was nice of her.
But though there’s an huge literature involving erotic scenarios between naughty nieces and their devilishly handsome, though wicked, uncles, the scenario seems likely to be disastrous in practice. And I’ve never fancied my sisters. No offence, if they ever find this blog; they just aren’t my type.
Anyway, incest is the last of the reasons I can think of for not having sex.