
I just realized the twins and tomohiro(?) has alpha-omega parents.

Yes, they're in a world where "anyone can get pregnant" (it's mentioned in the Omegaverse Guide that shows up in the beginning of some chapters). That's why the grandpa made the comment that he thought about Hiromu getting with Matsuo. Basically Alphas are the "elite" and many have an old-school/ superiority mindset where they feel that Alphas should only be with Alphas, to ensure that their kids also come out as Alphas.

It felt so different after re-reading the chapters all in one go rather than waiting for the update one by one. I don’t remember crying this much for hyesung.
Its like one after another, from his abusive father, being left by his mother, gambler grandma, grandma death, mistested second gender, has to leave school because the father left him, never been compliment as a child till he even scared to show that he is actually good at maths, awaken as omega, has first heat only for few weeks then suddenly got pregnant, got baby then suddenly knew that he’s bonded. He hasnt yet get to come around he’s not an alpha but an omega suddenly bamm pregnant.
He knows how much he has been hurt, he even scared when dojin told him he loves him when he cant even understand why would dojin likes him. He scared that byul gonna turn up like him, he scared that dojin’s family might not like byul.
There’s a saying that if you don’t even love yourself how could you love someone. Hyesung probably fell that way with dojin and byul. Hope that all his wound will be healed soon with dojin and byul also their family and friends around him.
This pretty cute