So basically there is this guy I have liked for a while and we have been staring at each other and all. But these days he seems ind of down. like... he doesn't look at me he became anti asocial he doesn't even talk with his twin, he never smiles. I want to go and ask him whats wrong but he just sees me as a stranger. I'm worried as a person. I would be worried if it was someone else too... I just don't know what to do. I want to be his friend. If a stranger comes and asks whats wrong you just say nothing as a reflex. But I want to know whats wrong. His twin seems kind of down too but not depressed... So Dollars basically I want help this guy. What do I do? How do I be his friend?
Thanks.

Maybe you should take a chance and walk over to him. Start up a conversation. Probably about something he likes. And then once you feel more comfortable, ask him if anything is wrong.

Agreed Kanra, try finding the right opportunity to talk to him or make one yourself also if you're willing to, try asking his twin or maybe mutual friends. Since it seems you truly care for this guy I think you could really form a bond with him not just anyone thinks the way you are right now and i think the latter would appreciate knowing someone cares. Though this is my personal opinion and i wish you the best in how you approach this matter.