How do I cope being ignored by my house mate?

I'm 17, depressed and have just moved in with my friend, her brother, sister and mum. It was perfect at first but now 3 weeks on her brother has grown to dislike me. He won't tell me why, just ignores me all the time. It's really hurting me and I'm lost for ideas what to do. If I move out I'll make myself homeless and have to go to a hostel. What should I do and how do I cope through this?