My brother lives with mother- she insists on this. This mess has been brewing for a long time- since I grew up there (me and only sibling are in our 40's). My brother's mental illness has always "the roost". Per my mother's rules, everyone must defer to him since "he can't help it".
In addition to having a mental illness, he is also abusive. Now that he is medically needy, he is primarily verbally abusive. I feel the abusiveness is a separate issue, 1. because obviously most people with various mental illnesses are not abusive and 2. because he can seem to curb these behaviors (now pretty much limited to screaming and demeaning her and anyone else he feels he won't get in trouble for abusing) in the presence of people outside the family. Since he can turn that off and on, I'd say the abusive verbalizations are under his control and not a symptom of poorly (now untreated) mental illness.
I live in another state and have responsibilities to my family which prevent me from going back to my former role of trying to run interference between my mother and brother. Being there growing up came at a high price to me as I am diagnosed with PTSD from the chaos I grew up in.
My mother never allowed "outsiders" to intervene. According to her, only she could properly manage my brother's issues. So when the opportunities for a more structured living situation that might better shape my brother's behaviors (this was back in the 80's), she declined that preferring to do that in house.
Now that her health is declining (she has cancer), the whole situation is obviously not better. He drives home health workers away from caring for him. I would not doubt that his being there impedes her getting what she needs too, though people do still come in.
She would never come live with me, and I am told that unless she is deemed incompetent, I would not be able to require her to do so. I realize that with my own responsibilities I would not be able to manage her day to day care, even if she would agree to that. She does have friends and non-family care givers in her area. None of us know what to do to make this better.
Reading the wording of her state's adult protective services laws, if she tells people to "mind your own business" and declines care, we are prevented from doing anything. It is clear to me in retrospect that she likely has her own mental health issues (prior to the situation of caring for my brother as an adult). Still, it is improbable that she would be deemed incompetent.
Thank you for any input you can give. I have always told people my only inheritance would be an endless list of problems to fix. Seems this has come to pass.