The guy I've been seeing punched my brother, how should I handle this?

Anonymous
A group of us went out to celebrate my birthday, the night was going well until the end. My brother, me and the guy I like (we'll call him C) were on our way home it was around 4am and c was driving. We were all having a conversation which was light hearted about people sliding into dms which is how C and I started talking. My brother was intoxicated and ended up saying to C that he was seeking validation from me and was pushing C's buttons. My brother is the kind of person who will continue to push buttons when he knows he's found one and C told my brother he was getting pissed off and to stop the convo. My brother carried on being argumentative to the point c pulled the car over, got out and told my brother that if he gets out the car he's gonna punch him. my brother gets out the car and C punched him. My brother didn't fight back at first and tried to talk to him but once C turned his back my brother took a swing. They eventually stopped fighting and we got back in the car and finished our journey home. My brother was trying to make light hearted jokes about Cs punch, praising his punch etc. He gave my brother a black eye and when we got home he ended up going home which is a 2 hour drive and didn't say bye to me. Today C has been very remorseful, apologetic and says he feels embarrassed and disappointed in himself for allowing himself to lose his cool. My brother has seen that he was warned but believes C is still in the wrong for his reaction. I dont know how to handle this situation, I really like C he's been nothing but amazing to me and I found out my brother had been winding him up all night because C didn't wanna pick up girls with him. Both are in the wrong and didn't listen to me when I tried to diffuse the situation. C has apologised for putting me in this situation and I don't know if I should be choosing sides because I see where they're both at fault. What should I do?
The guy I've been seeing punched my brother, how should I handle this?
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