Why is my cousin being rude to me?

Sorry to say but it sounds like he was making fun of you. Maybe they thought you were too nice a person. I know that sounds stupid to say but sometimes people are just like that. He is seventeen and they seem to make fun of everyone at that age. He was bored and would rather do something else then be with you or even his parents. I do not know why they would give you the cold shoulder too though. I think it was very rude of them all. I certainly would not go out of my way again to feel the way you do about it. I also would not worry my mind about how they treated me either. It just sounds like they are not very nice people to be around.