I would just set him straight if he was a friend.. is he a friend or an acquantance? because if he was my friend I would tell him he was a piece of shit and he better straighten up or he'd lose me first then her later cause he's an asshole... It's not your business to interfere if the two aren't really that close to you as Klinton said.
I don't like shit like that..it's one thing if they aren't vocally commited I suppose, but another if they are moving in together and shit.. The guy's just on a power trip..it's not really your place to tell her what's up, because if her eyes were open she'd know..and I'm sure will find out about at some point..
Just tell him you don't like it and if he says "fuck off" then what kind of a friend is he..more like a piece of shit...IMO.
