Borderline Personality
Questions posted in the Mental Health forum are being answered by Dr. Roger L. Gould, author of the Mastering Stress and Depression program and affiliated with the UCLA. Department of Psychiatry. Topics covered include anger, attention deficit disorder (ADD), bipolar disorder, dementia, electroconvulsive therapy (ECT), learning disabilities, memory, obsessive compulsive disorder (OCD), panic, personality disorders, phobias, post-traumatic stress disorder (PTSD), schizophrenia, stress, transitions, and work problems.
That said,there is not much for you to do about it...it is a mental illness, but it is also hard to treat. Medications can quiet things down, but the nature of the personality is that it usually causes the kind of family split you have described. It might be useful for you and some of your siblings to sit down together with a family therapist to see if you can heal the family split.