Responses
Oh no sorry, maybe assaulted wasnt the right word for it
His father smashed something on his head (if i remember correctly it was a trophy) and Yohan got inconscious. It was so bad that even year later he still have moment where his head hurt really bad because of this. And it's also probably because of this that he have such a short temper and memory issues

For thoses wondering, Yohan's family is complicated. Yohan doesn't really see himself as the favorite because for him his father is just a hypocrite (which is right). But if i remember correctly his mother do care about him.
His father assaulted him when he was in middle school but no one know about it except his father and the housemaid (Even Yohan doesn't remember it).
His parents do care to a certain extent but Yohan is a weirdo in general and they also care very much about their image, but since Yohan is complicated they "exclude" him to keep the perfect image their family have.
In the point of view of Yohan, he doesn't feel loved by them that's all