Hiya
I was bullied for years in primary school, and I was constantly told by my family (parents and all older siblings) to 'stick up for myself', problem with this advice is that If I could have stuck up for myself, I wouldnt have been bullied in the first place
so this advice just made me feel even more worthless.
I believe I was bullied because 1. I was incredibly shy and had zero confidence, 2. I went to school stinking of parents ciggy smoke 3. I was scruffy, I wore old knitted jumpers and same skirts/shirts all week. 4. It was a rough school in a rough council estate.
I was too shy to join clubs, and I certainly had no encouragement from anyone to do so, goodness knows how I got through it. Finally a rare friend told my teacher, who put a stop to it straightaway. (my bullies always warned me not to tell anyone - and I didnt) My parents never spoke to school or parents, even when a girl close by scratched her nails down my cheeks and left me bleeding and screaming in the street! My siblings were all leading their own lives.
I think the karate Idea, is fab, as long as your brother will do it, If the bullies know about it, that might be enough. It sounds like your giving him all the encouragement he needs. I cant give advice about contacting schools, etc but just knowing he has a brother who at least listens and cares must mean so much to him.
Do you know of anyone who has younger brothers, who are quite tough? who could warn these bullies off?
Good luck, and Hugs to your brother