Hello,
Sex in RPGs is possible. Just don't let it take over the game.
I think it all comes down to a significant part of storytelling.
Love stories have always been popular.
So look at it as a challenge to your storytelling. If the player wants a love story, then give him one.
One GM I played with watched soap operas and then took those elements and incorporated them into his games. One of the players loved role playing relationships. He had a gorgeous girlfriend (who he later married), so it wasn't about his being repressed.
Just a few ideas.