Yep. Has happened a few times and oddly enough most of the time those people have already died. Most recent is a (living, ofc) colleague of my dad who is married to a woman. For the deceased ones I had Princess Diana notably, for some reason, ate her out on a wooden floor of some room (??) although I'm very much not into blondes. But also one of those strange sexual dreams with dead people was my most vivid dream ever.
Back in my early twenties I had a thought about one of the Night Witches who made it to the 2000s before passing away from old age. For no apparent reason at all I had some sexual thoughts about her even if she wasn't quite my type. Figured I'd just get it out of my system by lucid dreaming but it didn't happen, so I fell back asleep. Had no idea I was about to experience something absolutely mind shattering.
It was in a bed that felt like mine but it was in a room that was all white and the lights were kind of blinding. She was on top of me, we were making out, all naked. We had probably done stuff before that I did not remember, it felt like the after of something. I literally could feel her size, her weight, her skin, the warmth, the taste of her lips, it was simply bafflingly hyper-realistic. And so full of love. Literally never felt so much love in a single moment. We had a short exchange of words and then resumed making out really slowly. When I woke up I was almost disoriented.
I carried the thing and a secret obsession for said lady for a solid two years, though it didn't prevent me from getting crushes on others in the meantime and was ready to give her up every time, but it did not work out and she remained with me for another year, up until I guess I processed it all. I'd write to her in my diary and all, went on a sort of pilgrimage while on my trip near her hometown and looked for her grave to sit beside for a bit, although I didn't find it. Made a little altar out of an old hardcover book with her picture and a few symbolic objects that I associated to her. Still got the little thing, haven't opened it in a while, though I do like to do so every now and then and light a candle.
This turned spiritual lol, but I couldn't not mention this experience about sex dreams. Still the most incomprehensibly vivid one I ever had. And it had to be a sexual dream. lol