How do I stop my older, physician brother from "advising" my mother about her health since he has a lapsed license?

His lapsed license is due to some emotional issues he has as well as the most important issues: trying to control my father's health care while not honoring his living will. The hospital he has worked at for 35 years is requiring him to meet certain standards before the license is allowed to be active again. My father had strokes 35 months ago ,was mentally alert, but could not live without machines. He was in constant pain and wanted to be allowed to die as he had dictated in his living will. Instead, he was moved to 8 different environments in my brother's quest to cure him. My other siblings would not become involved, but I was approached at each facility with complaints about my brother's interference. That included numerous complaints when he was at the hospital where my brother was employed. Both of my parents are/were in their eighties. My mother would not become involved with decisions because she stated that she was too busy and my brother would do what he wanted in the end. However, in the end, the hospital forced him to remove himself from the situation, and the administration asked me to handle the situation. My father had also asked me to make the others honor his DNR. I did, and he died with me holding his hand. My mother refused to believe he was dying and left the ER to go home. My other siblings, who were hours away or in other countries, could not understand why I was involved or why I spent the 8 months my dad was ill at each place taking care of him. My husband and son helped a great deal.
My mother has numerous health issues that need to be taken care of immediately when she becomes ill. My brother does not live near us. He is almost two hours away. Mother needs doctors that use the local hospitals,also. Any ambulance will take her to the hospital nearest to us. My mother is declining in her ability to make choices and does not want to considered old. I used to respect my brother a great deal. I am now afraid of his misuse of power. I am a retired Sp. Ed. teacher and have some minor knowledge of medical issues due to 35 years of teaching. I am younger than almost all of my siblings, and we really don't know each other anymore. I am afraid my mother will die due to this situation. I don't want to hurt my brother, but I don't want a repeat of my father's living hell. He deserved better and so does she. Mother has not given anyone POA yet, and can make her own decisions legally.