That we know of...
I mean, considering the fact that we only have the version of that bumbling boore narcisistic father of her's; I wouldn't take everything we know at face value. Just to name another example, he also claimed the mother was madly in love with him and conspired with the granpa to marry him, and it turns out she never did and contacted him repeatedly to fix the issue but he (being a narcissist) thought they were love letters...
I think he is a big baby and pity the granfather who had to try and raise that into a decent human being. His failure is clearly not out of lack of trying, he was just THAT much of a lost cause ╮(￣▽￣)╭
PS: I bet all my money knowing his character he was probably just horny and/or drunk and sa the mother but blamed it on an aphrodisiac cause he is "the victim" of a conspiracy ┑(￣Д ￣)┍
Isn't the grandfather really the biggest villain though? He forced the two people to get married against their will and then even drugged to his son with aphrodisiac to make them have sex, so it was basically rape. Probably kinda justified that he was murdered. Not excusing the dad for being a piece of shit in general though.