Did I make my friend break up with his girlfriend?

Yup. You excepted his affection and returned it. He did the right thing by immediately breaking up with his girlfriend. Don't fret about if you should get back together with your ex - you already have, just go with it. You two sound like you work for each other. Cheers

Well, if he was making out with you, I would say that he probably was going to break up with her,anyway. But you probably clinched it for him! I would just enjoy your new relationship with him, and don't worry about her. It probably would have happened anyway!

No, you did not make your friend break up with his girlfriend. This was his choice. He realized this in the midst of his relationship, which is why he ended it. This is a smart thing to do, since it is bad to lead someone on with the idea you care about them most if you actually care about someone else more. It is also not best in terms of expressing your own feelings well.

If he is kissing you, his feelings towards her are probably more ambiguous than he had let on with her. Or else, he may just not have had a strong commitment and decided he wanted to let that go to pursue something he felt more strongly at that moment.

As to whether or not that persists, I don't know, but whether or not it does, he'll have hopefully learned something about impulsiveness and about exploring emotional connections better. I have to admit, I don't think it was good to start making out. Obviously you don't do that wholly on the spot, you feel a longing to. When you decide to give in to that longing, you should resolve yourself with it.

I think acting on it right away was a bit cowardly. See, if you rejected his make out session, who knows whether he would have broken up with her. He should have broken up with her first, and then tried, because if he's willing enough to try, he should realize he doesn't have exclusive feelings for this girl.

I can quite understand succumbing to feelings for someone you have loved before. Knowing he was in a relationship, I do think you should have resisted kissing him until he breaks up, because you generally want a guy who loves you strongly enough that he wouldn't just go back to his current girlfriend if you refused him.

It does seem he wants you more, but I think it should be more about wanting you exclusively.

But in the end, while neither of your conduct was ideal, the blame is his, he is the one who chose to leave her. Your only mistake was giving in before he clinched it as an afterthought to your acceptance.