Thanks for sharing your story. You have a right to be angry as you have been forced into a position at a young age to be what is called, "a Parentified Child". That is, you were forced to grow up too early to care for your parents, who have limitations that prevent them from being effective parents.
However, you have a brother who seems to get off scot-free, and hence the anger continues. The best way through is to acknowledge the role your father played in your life, then your mother's role, and finally your brother's role today. You will need to learn to set boundaries against your mother and your brother - this will help you get back a sense of control, and the anger will lower. Then you will be able to start the grieving process proper.
It's also important to look at both of your parents' background -- this often will tell you how this problem has been transmitted through the generations. It's important to understand that at least your mother and your brother are not operating from an adult position, and therefore you cannot have close or healthy relationships with them. This, then is a source of anger and loss. Understanding this condition is a key to getting out of the physical and emotional prison you feel yourself in -- however, I can assure you that no matter how you feel, you are not powerless. And your mother's power is an illusion. You are likely the most functional member of your birth family and I would encourage you, if you haven't already done so, read all the articles on the main site on NPD. Knowledge is power. If you need help in starting to unravel yourself out of the situation contact me through the main website, either at Enquiries, or through Services. It seems huge, but Cathy you actually have the power here. At least your mother is in assisted living, but I understand the emotional blackmail that narcissists are capable of. However, they have no real power at all, it is a web of illusion that starts when you are a child and that is why it seems so powerful even as an adult.
B.Sc (Hons). B.Psych. Dip.Sc.
Principal, Your Online Counselor