Sorry I can’t help you with that specific manga because there’s quite a few that come to my mind but your best bet is to look for break up yaoi manga lists and read the blurbs. Iv read a ton of yaoi that fits this and they’re on my list, I hope you can either find it on my list or find a list that has it!
http://www.mangago.zone/home/mangalist/525526/
(That’s my list hopefully it’s on there! Good luck! )
Maybe "Hate mate" or "Lover Boy"? idk i'm taking wild guesses. Here are the links if you want them: http://www.mangago.zone/read-manga/lover_boy_lezhin/?av=3 >>lover boy
http://www.mangago.zone/read-manga/hate_mate/ >>Hate Mate
I can only think of:
http://www.mangago.zone/read-manga/the_baker_on_the_first_floor/
http://www.mangago.zone/read-manga/wistful_summer/?av=1
But try looking for it via tags: http://www.mangago.zone/tag/marriage/
doronuma?
Got you, suna no rasen
I can't remember what it was about I just know that uke's ex left him and got married with their friend. Uke was getting over him with another guy and ex realised he made a mistake. I remember that he promised him that they would be forever together and then the wife happened. Uke doesnt want him back and is aiming for the new guy. Im sorry if this is a mess Im writting this in the middle of the night because I really want to know.