I was in a relationship w/a man w/BPD and believe me, it was no picnic. I was beginning to think that I was the one w/the problem until I started researching on the internet and when I approached him on the subject, he admitted that a psychologist told him that he was BPD and he had been having phone counseling sessions for years. I still tried to make it work but, as you say, there is no cure, only treatment, and they have to want it. He didn't want it and I'd had enough of his manipulation so I ended the relationship. It's an even tougher situation w/you because it's family. I don't envy you but I admire your courage and strength.