My cousin hates me and won't tell me why! And he hasn't talked to me in 1 1/2 years! What do I do?

I'm sure he doesn't hate you. He might even like you and is shy? you should try getting someone else to ask him for you, maybe he will be more open to him/her. Or send him a message telling him how it's making you feel that he is ignoring you and what you can do to get his friendship or trust back whatever the case may be.