@etherial2
I'm sorry to hear that you find yourself in this very difficult situation. Not fair at all.
I'm just going to speak a little bit about the experiences I have been through with my sibling where I have the benefit of looking back in hindsight of what I went through. It's never easy when it comes to family because you care about them but a big lesson I have learned, as the saying goes, you can lead a horse to water but you can't make him drink.
I suggest you help where you can without having anything affect your own life. It is all too easy to become drawn into someon else's dramas and mental health issues. I don't want to sound harsh but believe me when I say that sometimes, if you can, it's better to stand off to the side. I firmly believe that GPs and the mental health services should be there to step in when needed. I've come to the point in the past where I had a huge shouting match with a mental health professional because my sibling clearly wasn't getting the care they needed. Don't be afraid to jump up and down a bit if you feel it's necessary. Make the phone calls and be persistant.
Another thing I learned which I wish I had known a while ago is that you are only responsible for you, not anybody else, no matter what they are going through. If you are copping the abuse you need to walk away. If you don't feel safe with any of your family then please don't put yourself in a position where harm may come to you. You owe yourself more than that and you are worth more than that.
As for Bro1 going off his meds, unfortunately there is nothing you can do about that. Him bragging that MH can't tell that he's not medicating is typical behaviour for someone with this sort of mental illness. They get very good at convincing people that things are just fine and dandy when the reality is completely different. It's not until they hit a wall and spiral downwards when they become open to asking for help again. Same thing happened with my sibling. To the outside world everything was just smelling like roses yet life at home was al living hell.
I'll wrap up in saying that I think you should show your family that you love them and will be there for them but please tread lightly in how much of yourself you're willing to give.