I have an Essential Tremor, I was diagnosed in high-school(I was 13, I'm 19 now). Good news I find that my tremors come less often, when I was younger my hands would shake nearly all the the time. Bad news my tremors have gotten worse, when I was younger I could work through them, now I have to stop what I'm doing or really struggle. This will be a life long thing for your brother, I hope that he is able to do what he loves for as long as he can.
There are medications for Essential Tremor, but nobody knows how well they actually work for people