Help please. I cannot find this manga!

I've been trying to find a manga obsessively this week. It was about a boy who was saved by his sisters future fiancé, and he fell in love at first sight. Well the sister and guy divorce, so he ends up making his move on the guy.the kid ends up living with him, and finds a picture of a women. Turns out the women was the guys old teacher who had died, that he had fallen in love with when he was younger. I can't believe I can remember a whole plot but not a name. Please any help would totally be appreciated.