My girlfriends ex is wounded? he is my firend help?

to cut an extremely long story short my mate broke up with his girlfriend then stepped aside so me and her could be together(great guy i know) but i didn't ask himto make that decision. we all chill in one bid group at the pub most nights therefore me with her infront of him. i know he's unhappy about the situation but he doesn't show it. we are very close mates and used to be able to talk anything out especially after a few drinks, normally i'd talk to him and help him sort himself out but this time i'm part of the problem what should i do? talk to him or leave him to stew on his feelings