So after a long time, I've finally met up with my brother again but things are very tense. It also doesn't help that he's the type to not express emotions. What should I do?? I want to talk with him but he makes it seem like I annoy him with everything I do.

I suggest trying to find something both of you are interested and then try to start up a conversation about that and he should be more likely to open up to you

I would suggest telling him what you said here and then asking if he even wants to "reconnect". It is pretty likely he has the exact same problem and also doesn't know what to do about it. And if he doesn't want to, there is very little you can do to make him friendlier with you.
If he does, I am sure you can figure something out together. From topics you are both interested in to things that just break up the tense atmosphere (usually bad jokes. Very bad jokes.)