My little brother would like to play the Combine but I don't know how to register him without getting banned. I did send an email to the multi accounts people and haven't received one back what should I do now
If your brother is playing the same net connection as you, simply have him sign up, and put your name into the field for multi accounts when he registers. This should tag it so that the acceptance people will leave it for the multi people to have a look at. You may have to send the multi director an email, depending on what the rules say.
If you sent an e-mail, and if he enters your handle in the appropriate field, you should be good. Even if you get flagged by accident, you can refer to the previous e-mail to cover yourself. Avid might even adopt a stray kitten by way of apology, if he screws up! ;)