Your Partner And Your Sibling With Borderline Personality Disorder
Don’t be angry over the secrecy
It will eventually come out that your partner knew about this. You may be angry—fuming, even—and insist, “You should have told us! We need to know these things right away. It’s the only way we can help her!” But try to understand that, he didn’t understand the severity of the situation, and he just wanted to win brownie points with your sibling—a fact that she very much took advantage of.