Trying to find an "old" BL

I've read this one a long time ago and cannot remember the title for the life of me. Please help!

It was between a blond and black hair guy the black hair guy was older and they knew each other since almost little.
He was a drawing teacher and had an atelier where he was teaching people the blond guy was in university and signed up to take his class because he actually was in love with him for a looong time. But the black hair guy had an ex wife which was why the blond guy never really pursue him before that.
He admit his feelings to the black hair guy who totally reject him bc he find him to be too young. The blond guy is crushed and end up discovering that he have a fwb so he somehow convince him to also be his fwb. Black hair guy take it on him thinking he wont go through with it but he does and he is mind blown by the sex they end up like this a while they fall in love there is this whole story with the ring of his wedding that the black hair guy keep and seem to not want to separate from it and it cause some drama between the 2