Need help finding a Manga

I read this manga where there are two boys that look exactly alike but one has blue eyes and the other has brown (i think) and the girl who likes the prince-like smart one was fooled by the bad-boy one into believing that they are really one guy with a split personality. Then when she realizes that's not the case starts hating the bad-boy one for that and stealing her first kiss? After a lot of trouble and MANY chapters she finds out the bad-boy is not so bad. The smart nice boy leaves her (they had started dating) for his best friend who needed him (which I remember being super pissed about) and she ends up with the bad-boy. They have a son and a puppy later on.