Ok whats going on why the duke punch the brother?

Someone mentioned that Camellia had bruises from the binding of her chest that is why duke got mad...

Oh no wonder ,did he hit his brother because his brother couldn't protect his little sister?but isn't the fault lies on his mother?that bitch should be the one need to punch dammit

Didn't mention but yeah the bitch mother and the useless father, anyways hopefully they'll get a bad ending (fingers crossed