Is our "friendship" ruining his relationship?

well from a guy perspective this happened to me once but i was in your friends place , and i think he might actually like you , since after being so close friends you got to know so much about each other and now you know everything there is to like/hate about each other . So maybe he cares about you even more then her...and not in just a friend way . hope this helps , but hey its just my opinion .