User blog comment:Commdor/Questions for Mass Effect 3/@comment-65.166.101.165-20110109070312/@comment-217683-20110109071101

That question was actually already answered way back before Mass Effect 2 came out. Casey Hudson talked about it in an interview, which we link to on the Romance page, and he did state that there were going to be consequences if you didn't stay faithful to your romance from the first game.