Should I contact his family

I was in a relationship with a man for 2 years. Found out he was drinking that whole time and I had helped him through several mental health crisis situations and each progressively worse. His last one he got sober and 10 days later told me he wanted to be able to talk to other women and got on a dating app. I have been his sole “caretaker” and he used me for emotional support and regulation. His brother learned about his mental health and drinking problems with his last spiral because he had to pick him up and take him to the hospital. That day he learned about me simply as a “friend”. His brother knows I’ve been his support for a long time. Well I have blocked this man because of cheating and admitting he wants to be with other women. Because of the multiple self harm threats, should I notify his brother that I am no longer helping and am no longer available to pull this man out of these spirals? He won’t go to therapy. He is just using women as a distraction and I am angry but I don’t want him to hurt himself. He told me I am crossing boundaries regarding reaching out to his brother. This was before I blocked him. I am not in a relationship anymore. Should I walk away or message the brother. I would have to reach him thru a social media app. I don’t even have his phone number. I still have his g*n that I took away from him.