It's yaoi and the story goes how the sister of mc married this man and that man also had a son. So the mc became the uncle for that son and they got together. For more details the boy aka the son has blonde hair and the mc has black hair. hope you guys can help me :) i want to reread it and if I'm not wrong it's completed!
https://www.mangago.me/read-manga/my_housemate/ is it this one? It kinda sounds similar
can anyone give me the link where i can read the novel? ┗( T﹏T )┛
https://binnovel.com/novel-book/debut-or-die