Unfortunately, someone has to play the "bad guy"
Benefit of the doubt, it's probably so he's aware that the child still feels that way (he did say Gyuyoung never brought it up). A child as young as Gyuyoung shouldn't have to hide he is sad about this and that, regardless of what the topic is. Also, the husband also wants one more. Unsaid expectations lead to resentments, even if he is choosing not to bring it up because of this and that.
From what i understood, the immediate family are not expecting anything. It's the grandparents that are being extra honestly.
The other father stated that while he wanted a second kid, the desire to have one should be vocalized by his partner, not him. And their kid understands his birth father's circumstances. While being sad about that is ok, the way the grandparents handled this whole situation isn't. I can agree on the kid not hiding his feelings but opening it with "are you really not planning for a second kid? My grandbaby is sad he doesn't have a sibling he wants it bad" is such crass behavior. Pretty sure there other ways to convey the message better.
Pretty realistic in an old-fashioned asian household if you ask me (as one myself). Very spot on actually, if anything, I'm surprised they aren't pressuring them more. Not saying it's correct or I agree (I don't) but seeing as they even covered up him being an omega regardless of any repercussions in the first place, urging him for a second child seems low on the list of wrongs sksks

Everyone knows the context, and that's why the kid isnt bringing it up anymore. So why did you have to? What are you trying to achieve here? Guilt trip him into having a second kid? Smooth brain behavior christ.
Yes, i am aware surrogacy and adoption are options, but it's callous to bring up the topic of children when the pregnancy journey redhead had wasn't smooth sailing, and he didn't want any more. Even the alpha wanted a second kid, but he doesn't push it outside his freaky bedroom talk.