Yes he was definitely crappy. However, he seems to have genuinely believed Castiel was doing well and that he was better off without his presence
Why he seems so nice to the MC? I think it's really that she enabled him to see the abuse and *CRUCIALLY* says outloud what she wants.
Castiel is understandably hesistant and shy. Also, his abusers told him he was hated by his dad, so he rarely appeared in front of him and is only *NOW* slowly saying what he wants...Through the MC.
If there's anyone who should be criticised it should be the king!- He *KNEW* his son was bullied and abused, but it seems he didn't do anything about it....At from what the flashbacks suggest (︶︿︶)
Every manhwa like this always gives the MC a neglected older brother whom for some ungodly reason the father just could not have cared less about until the MC showed up. And even when they DO start SORT OF caring they just treat him like an extra and still give most of the attention and favor towards the MC. So you mean this new child was worth trying to be a decent dad for, but the first one wasn't???? and then what's even crazier is that the brother magically seems to never be bothered or recentful for this blatant favoritism and instead somehow joins the blind-love-towards-the-FL band wagon. I just can't ever enjoy those family dynamics in the manhwa. Treat your children equally.