I might be batting in the wrong field but would anyone be up for something Johnny and Daniel related from Karate Kid/Cobra Kai?
Could go darker with it, hate sex, punching and kicking before or during sex, cheating since Daniel is married, etc.
Or go fluffy and spin off of season 2, let them patch up and have the chance to be friends, start their own combo dojo, co-parent, etc
Or something similar. A couple of old high school rivals (karate or not? idk what else might qualify unless they were jocks from rival schools or something) who meet again and tension and feelings flare. If taking the PB route, they could be any age, really.