"Have any of you male or female, ever had filthy fantasys over your friends partners?? X "
Too many times.
My ex mrs used to bring all her hot girlfriends round the house.
Used to drive me nuts. Kept imagining mffff scenarios in my head.
Not friends so much, but definitely colleagues’ partners. In one job, I was PA to a director. I also had a huge crush on a director from another office who used to come to our office quite often. It was a bit of a shock when someone told me he was married to my boss!
We had a threesome with one of my girlfriends she wasn’t a swinger but we talked her into it , actually it’s best left as a fantasy it complicates the friendship