Do guys not wear briefs anymore ? Watch
I'm going to assume you're a female as your name is "kate". I'm sorry for saying this but for boys their type of underwear REALLY is a big deal. He needs to be wearing boxers by now and I think that if you liked your brother at all you would try to side with him. Can't you see he's being picked on? If I still had PE lessons and a boy was wearng those nappy looking things you can be certain that I and everyone else would roast him as he should have ditched those things before he got to secondary school.
Don't be so dramatic, what boys wear underneath doesn't matter at all, only those who are scared and insecure will make a big deal out of what another boy's underwear preference is. Supposing you wore them, are you going to cower in fear because others don't like what you do? If you go about trying appease another's sense of normalcy then you're robbing yourself of what makes you who you are. Briefs are short and yes they do put a bit of pressure on the genitals, but they fulfil their purpose. Boxer shorts are restrictive and they cover you up more, they look the same as similar kinds of underwear whereas briefs look distinctive.
Ok we get it you're very tough, whoopee, but if a child is getting bullied and teased over something they can change easily they may as well just conform to avoid all the drama. Not everyone is trying to be "distinctive" or trying to make a point about being different.