You are very blessed with your beautiful family.
My two cents is that your brother has to understand this is YOUR appointment and he is there for SUPPORT.
So I agree he needs to be educated on CRPS BEFORE he goes so he undertands this is not an in your head disease.
Also, if he has personal pertaining to you and CRPS questions, which seems he would be that nice of a brother, he has to WAIT until you are done with your questions and concerns. Until you are comfortable with the knowledge given to you...maybe give him ONE question. Meaning, after he's up to date as best as he can, he be allowed to ask the doctor ONE question. Something ready before the appointment.
If my family was that caring and wanted to be this involved, this is what I would come up with.
But whatever you all decide please keep us updated......