@Scholtz It is abuse if he always gets beatings in that form, without that someone takes his side. More often then not people who get abused by family dont defend themselves, because they are "trained" that they deserve it. That can even happen to adult people and is by no means something that justifies all of that.
If the dad and family would make the siblings compete with the MC in terms of Magic or something like that, then it would be another thing. But that doesnt happen and it is more like, that the father doesnt want his son to be a mage. He is directly wasting all the talent his son has for magic, because the family are knights and the daugther and eldest son have talent in it.
At start they did encourage him, but in the last chapters they only hold him down and abuse him like that. That the father did go overboard to knock his son out is 1 thing and is taken as something natural without any form of acknowledgement that it was too much.
Also if we seee how MC is treated and NO ONE says anything to defend or praise him even though he did great things for their area.
Even if it is the kink of the Author, this doesnt make it better, on the contrary it makes it worse. It doesnt fit into the story and just makes it really really bad writing. Maybe go the classic and let him have a love interest later that he is completely whipped by her. THAN it would have a fun twist (even if it is somewhat standard), like this it isnt anything besides abuse.
PS: To the ones who think of this as hilarious and funny: IF the author wouldn't make it that the MC gets hit again and again and would have the same amount of good things, it would be different.
For example: He has a match with magic involved against his brother and wins rather easy and gets a bit cocky and then the father says round two without magic and the MC gets "destryoed" because he is so much weaker .... that would be funny and a joke. But like this it is not. Any sane person who says this is funny should truly question himself.