Pam, I'm sorry about what you're going through.

I'm estranged from my alcoholic brother and borderline personality/alcoholic sister. Even when they were sober, they were both incredibly difficult to deal with. I don't miss them. At all.

That said, I tend to agree with Lisa in that you might try to react to your sister with some degree of compassion--at least with the current situation. Your brother's situation IS sad.

Have you ever spoken to a therapist? I have. The day I decided to disassociate from my sister, I made an appointment and have been seeing her for about seven years now. A good therapist will help you figure out the right boundaries to draw and how to draw and enforce them. Ideally, over time, you feel more secure and are better able to deal with the difficult people in your life, often from a more emphathetic place.

Short of therapy, read The Dance of Anger. It's one of the few self help books I recommend.