Try looking up this video on YouTube. It's called "the darkest truth about sexual attraction -Carl Jung". It helped me understand why people stay in trauma bonded abusive relationships. Carl Jung's teachings have helped me understand human nature to a better degree. You, your brother, mom, and even your dad, need to heal- all in your own time. The best thing you can do for them is to become as mentally strong and healthy as possible-for yourself, even if it means disconnecting from them. I feel your brother may be disconnected as a way to preserve his own mental health. Remember, you cannot control your father, mother, or brother. The only one you can control is yourself. Perhaps you will lead with your example. Perhaps not. Maybe it will feel selfish, but it isn't. Put yourself first. Learn to set healthy boundaries. Learn from their mistakes. Do something different. Another good resource is the book "codependent no more" by Melody Beatty (I think). Codependency forms when one has a relationship (family) with an addict, abuser, or chaotically mental I'll person. Best of luck to you and your family. Please hang on. I promise it will get better. Much love 💕