I mean maybe It’s my density talking, but I didn’t really think he meant sex when he said “become mine” more like “don’t mention other people when we’re alone together” or “I’m jelly so I wish I had all of you just to me” just cause he’s been mostly decent and cares about her. Plus literally every one is home and it’s be suuuper stupid to try that kinda shit. He’s insecure and communicating his insecurities, he may be older than her, but he’s still a kid too. By talking they can actually do something productive.
Big question is if the fl can communicate and how well he can listen.