I hate that I know the answer to this question. :( But, yes, an attorney will come to a hospital and do a will. In my mom's case, I needed power of attorney and a will and a couple other documents and he asked me beforehand how my mom wanted it written up. She was of sound mind, so she was able to sign off on the will, otherwise, I'm not sure what could have been done. I want to say my attorney charged me about $500 for that. Your brother's will may be a tad bit more complicated because he hasn't received the inheritance yet. I'm sure others will have more complete answers for you. For me, the scariest part was just calling a lawyer and trying to understand all of the steps that needed to happen. Once I got over that fear, the rest was pretty easy. Good luck to you, I know that's a difficult situation to be in.
Oh, and as far as witnesses, I had one aunt and one uncle come to the hospital as witnesses, they had to provide their driver's licenses and sign the documents. It took maybe 30 min for the lawyer to go over the paperwork with my mom to make sure she understood and agreed to it.