beta
So the manhwa was already close to the ending huh, it's unfortunate that it never finished.
So, Cole's, Isaac adoptive father, marked Isaac, and manage to do so before Felix found Isaac, then Isaac told Felix everything, that he's Benjamin father, and that he was the omega 4 years ago. Then Felix found out about Cole's mark, and immediately marked Isaac to undo/stop Cole's marking, while on the process, Isaac ask Felix to save Benjamin and his mother, Felix is reluctant to leave Isaac alone because of mating process, but still follows Isaac request. After that, he came back to Isaac, then they've sex and finish the mating.
Then they got married
Then at the ending of side story 3, it seems Isaac is going to get pregnant again. But I guess it will be confirmed on the menu sequel, which is Love Benjamin.