16 years and their reason is 'autism'? Thought they'd have picked up on it sooner... Communicating and understanding is critical. Hard when you don't speak the same internal language. Many things are left unsaid even when synergy is high. People can be bad at explaining themselves and sometimes don't even understand their own feelings and thoughts; requires some investigation and testing.
If they aren't interested in making it work then that's that. But if they are, then you need to work on it together. Figure out what the problems are and how you can mitigate them, or if you even want to. Relationships can take effort and intention, and aren't always comfortable in the moment.
But I'm a spectacular failure in the love department, so what do I know anyways.