It may not be that he doesn't trust you with him, it's possible that he just feels very protective towards you and isn't ready for his 'little sister' to grow up yet. Maybe he still thinks of you as a child. Either that or he's a bit of a control freak.
If you have this boys address why not write to him and tell him how you feel? Don't go overboard with it, but just explain that you'd really like to see him and that you were unaware of his feelings for you when he moved a few years ago.
You don't mention your age here so it's a little difficult to say exactly what you should do. Perhaps your parents could help out here by asking your brother to ease off.
You could always ask the boy out to a movie or just a coffee somewhere public so that it's in a public area. What about dinner with your parents?
