Why does my son cry so much!!!?

I have twins that are going on 2, i have a boy and a girl. My son is the oldest but he cries about everything you can imagine! I mean its irritating all day long about nothing and im tired of it. when there is nothing wrong with him thats the worst. I need you guys help cause i can't keep listening to this evey day it's nerve recking and he's crying as we speak now and it's 2am its crazy. PLEASE GIVE ME ANY IDEAS I WILL TRY THEM ALL.