What to do when the flying monkey is someone you love?

Hey guys, I am so conflicted. I have been NC with my bpdmother and bpdfather about a year and a half. Since then I have had many milestones of which my GC brother was invited to you. Inevitably, soon after these events, I would get email, text messages or Facebook posts on my other family members walls describing the event and how they have been wronged. Some of the things that happened were personal and only few people knew of, including my brother. I asked him directly and he admits he has been feeding them info on me, sometimes within minutes of the events occurring even though he knows I am firmly NC.

I calmly asked him not to and his reply was the deserve to know and they are going to hear about it anyways. I tried to keep calm, but I ended up putting him on blast. I said we have an arraignment! I don't talk about your decision to stay in contact and you don't give me grief about mine. I told him our parents behavior is not normal, it is in fact grossly abnormal but it is hard to see because it is all we knew. I told him we are allowed as people to cut off people that are toxic to us, even if they are our parents. That he doesn't see what has happened bc he is GC and I choose not to tell him what they have done or said to me.

RBN, I am so hurt. My brother and I used to be very close but ever since I decided to go NC things have been very rough. I feel completely let down. I thought I could trust him but I feel like that trust has been violated and shattered. He is not a mean person but he is definately an enabler. I told him that if continues to tell them things about me I will go NC with him as well. He apologized and said he didn't mean to disregard my decision. But he did it over text and it didn't really feel honest. And even if it was, old habits die hard. My parents know he is willing to hand over information on me and will push to get it.

I'm sad and conflicted at a time when I thought I was moving on. Just need some support from other RBN I guess.