If you were a bit more specific it would make helping you fix your problem go a lot more quickly and easily.
(Exapmle Specific: I cannot connect to a netgame, and every time I try to, SRB2 shuts down and gives me an error message *insert error message here*)
Basically, specifics would be Error messages, Internet Stats, and stuff like that.
If you are banned, that means that the computer's IP address is being blocked. If you and your brother use the same computer, then if one of you is banned, then no-one can get on for a set amount of time. I'm not sure, but this might also work even if you have two or more computers (but they'd have to be connected by a networking system).