Worried about my brother

I feel like my brother is pushing me away. He is extremely depressed. His fiancé died several months ago. She was murdered by a friend. A few weeks before she died they found out she was pregnant which made them both so happy because he had a very low chance of ever being able to get anyone pregnant. I've been telling my brother its not his fault, but he convinced her to go hang out with that friend because she was feeling lonely. Me and him have been super close and I hate seeing him drink himself away. He's pushing me away and won't talk to anyone. He used to have suicidal thoughts as a teenager and I'm worried he's gonna try to kill himself to be with his fiancé and their baby. I'm not sure how I can help.