Tell your brother to go to a doctor, and one look from a doctor will tell him what it is most of the time? It doesn't sound like Genital warts if he gets it under his belly bottom and forehead, that sounds more like a heat rash, or Folliculitis inflammation of one or more hair follicles damaged by friction from clothing, but then again it doesn't explain the forehead, but bumps on foreheads are common.
It's usually ends up as nothing once you see a doctor. I think I once had a wart on my inner thighs and happened to be at the urgent medical center because I had a bad case of Strep throat and asked the doctor about the small white bump, he said it's a wart, acted like it was nothing, told me to ask my regular doctor to burn it off because they only handle urgent medical needs. So I just went to the local drug store, and got that wart medicine, put it on, and a few days it was gone, so I never went back to the doctor because of it. To this day I wonder if it was considered a genital wart, and if so how did I get it on my inner thigh? Did pussy juice roll down, or perhaps she was pounding on my inner thigh during cowgirl time?
Currently I have a small whitish bump on my ass, and I swear I'm still a virgin back there. I was concerned about it, because it was there for months, but I never saw a doctor about it, until I went to the doctor for another reason. The doctor of course told me to bend over and put my elbows on the table while he takes a look. He said it was nothing, it's only a 'skin eforum.xxx' and they are non cancerous. The thing is considered so minor, that insurances companies usually don't cover the procedure and I may have to go to TJ to get taken off if my insurance won't cover it, as I don't want to cut it off myself or have somebody do it and risk infection.
But like I said, it's usually turns out to be nothing, but it's best to find out from a doctor and put your mind to rest.