
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 (︶︿︶)

That's still not an excuse, the problem is still there. He doesn't want to parent? That's fine. But at THE VERY LEAST check on him to see if he's actually even still alive. It's the bare minimum if you aren't gonna be his parent. Because from what I could tell he DID in fact swing by the mansion every once in a while which means he didn't bother to even physically LOOK at him.The MC only voices things better because she's not even actually a child which basically means that if she ACTUALLY WAS he would've had no interest in her either and BOTH the kids would end up abused or even dead.

He or other brother characters in other stories don't necessarily HAVE to be resentful towards the MC specifically, but realistically speaking, put yourself in their shoes. Your father, whose love and attention you've craved your whole life (because you're literally just a child) has never so much as glanced in your direction. Now this new sibling shows up and suddenly they're capable of being a somewhat good father??? And yet somehow you're still only receiving the bare minimum of attention. Yes, TECHNICALLY speaking they don't HAVE to feel that way. But the reality is that it would 100% be the normal/natural reaction. Whether that is the "right" or "mature" way for him to feel means nothing, because again, he's just a child, he wouldn't know any better.

Hmm when I was young, I didn't get mad at my youngest sister for receiving more love from the adults. I just thought the adults were too biased and expected things too much from me. Ig I like my sisters because they were like friends from all the time we spending playing tgt. That's why I can see how Castiel felt like he had a new friend instead of a rival. Plus, he thought he was the problem, so he couldn't imagine someone else was to blame for shitty things happening to him.

no hhate to you or anything, but again this dude is clearly mentally ill and saw himself as someone who would harm his children mentally by being around them. once he realized that they were being mistreated, he fixed it really quick, and made an effort to be their parent after. it's not an excuse but it's a valid reason as to why he acted ike that, especially when he was out so long and nobody in the mansion said otherwise.
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.