I'm pretty sure that the reason why he's so bratty is because Kiel is literally his only friend since, looking at the last few panels, he seems to be a illegitimate son. Which is to say that he's lashing out the same way any other child would when the one person who's kind to you and doesn't care about your questionable status gets supposedly taken away. Ffs, he's a little kid, y'all calm down with literally wanting a child to get hurt because he's sad and scared.