Should I remain friends with Best Friends Ex?

Ok so interesting title but yeah that's my question. So basically, one of my best friends got broken up with a month ago by her boyfriend. For context, I have been friends with both of them for the past 4 years. I met them both at the same time and we became friends. They've always had a little thing between each other but it never became a relationship till last year. However, now that they've broken up, Im unsure how to navigate my relationships. Firstly, it was a bad breakup and my friend is in a severe no contact, and will absolutely not try to be her ex's friend, acquaintance, anything(WHICH IS COMPLETELY UNDERSTANDABLE). Second, I will admit that he has done shitty things during their relationship which I only got to know about after their breakup from my friend. Third, the only reason I am having a hard time cutting off the boyfriend is that he is also one of my best friends. Truly, in the most purest way ever, he is my brother. We aren't related by blood but I love him in a way I love my older cousins and we are super duper sibling like. He even said that I am practically family to him. So now, I am wondering if I should be friends with him cuz my best friend is uncomfortable with it? Again, I love her to death, she is amazing, brilliant, just ugh I love her. But he has also been a very important person in my life and i dont know what to do. Its not like I can even avoid him either cuz we are going to the same college, same major, same track and everything. So please, let me know!

Also, is it okay to ask him what he thought/felt during the breakup to just see what it was like from his side?