I read a time travelling book (very old and dusty, relatively short, I think it’s from the 70s) where the protagonists discovers over time that he is his own father/mother. He travels in time so often that there are zillions of him at different ages in each time.

He just ends up partying with himself because he can be just himself. And with all the drugs and partying one thing leads to another. Also because he travels so damn much somehow that leads to a female version of himself.

That Ethan Hawk film Predestination is a less fucked up, similar version of the story.