[WhisperingSilence]

Could your brother take some self defense classes of some description it will help boost his confidence and teach him self defense, so he can if and when need be defend himself against the bullies.

As the bullies themselves - the bullies sound cruel and mean. And to me it sounds like harassment and you could have grounds to get them spoken to by the police for physical assault and harassment.
I have found that with bullies that they often fear the police.

Maybe you could suggest to your brother that he records a diary of when the bullying happens, the names of the bullies and what they are doing so that then your brother has the evidence to take it to the teachers, police and school governors.

Self defense classes may also help him with his anger and give him a safe release for his anger.