Couldn't word it better myself
and hyesung don't even want to abandoned byul, he just misheard doujin and the fucker who end up with doujun. he literally scared that doujin would dump him and byul. he's literally homeless, had nothing. so he fled away. and that fucker keep telling shit to him while he live under that fucker roof. until he met doujin and realized that doujin keeps the baby. it's all that fucker's fault. and i hate how noone hating that shit, and hating on hyesung instead
Yeah, also. Hyesung never took the agreed money for giving birth to byul. The money wasn't even for the value of it, but a way for hyesung to feel emotionally safe from attachments since dojin wasn't exactly the nicest guy around. Who'd believe he'd love the child or let hyesung off from the way he acted on him. Hyesung initially had a good feelings for Dojin, but when he heard the Jerk (then) dojin talking like hyesung was some sort of usable inspiration material hyesung shut off any feelings for Dojin.
The deference between Hyesung and his mother is that hyesung never had a day that he didn't regret leaving byul and he never downplayed his mistakes even Dojin told him it was alright, even when he came back he couldn't forgive himself and no matter who forgave him, he couldn't. Hyesung's mom on the other hand not only acted like hyesung never existed, she abandoned him and put the blame on him after telling him that she heard he didn't want to see her, so she didn't.
She raised hyesung longer than when hyesung left byul, yet hyesung had more emotional attachment to byul who he'd only see once and came back for him. The mother didn't, he raised the kid for a few years, left him and lied about not having a son, never once went to see him.