He's just not good enough for her. It's not her, it's him. He worships her, for she is more himself than he is, and whatever stuff souls are made of, theirs are the same. They'll try to stay friends, although his heart will pang with the tender jolt of unrequited love forbidden every time he sees her at the park or protesting in front of city hall, and he'll eventually land up in jail for stalking and creepiness, where he will commit suicide because he'd rather die than live without seeing her face again and he cannot live without his life and soul and whatnot.
Apparently, this is yet another example of failing to fucking search. Quelle surprise, bring me some pearls to clutch etc etc.
It's really mean of you to tell the OP that kind of thing when the solution to their problem is much simpler. The male teen should marry the female teen's sister in law, then the OP should kill off both the female teen and the sister in law.