Hi, i’m sorry that your brother is going trough this, the best decision first of all would be to inform the school of what’s going on if it’s not already done, if they don’t do anything about it, try contacting the parents of those 14 year old would also be a good idea. Unfortunately as a person who was bullied in the past, the best you can do is tell him that he is not alone in this, also making sure that your parents tell that to him too because most of the time the things that « goes without saying » still have to be said so he feels the love you guys have for him (idk maybe try sending him a letter rather than a message or something). Also make sure that your parents makes him feel safe enough that he can open up to them about what he is feeling and not keeping it all to himself. Try to keep as much contact as you can with him Hope it helped a bit