i felt bad for step brother cause he became the same as aria who was manipulated to do bad things. What aria is doing now is baiting him but I agree he shouldn't have tried to lock her up.
For the dad I was also surprised and than not. Usually the moms are the evil one trying to get fl and ml apart. But in here the dad is thinking of connections he will make with aria and the prince. We may say oh he is shit because of that but we saw what happened when cain became the master and when their money was squeeze dried from aria and mothers scheme. It's tough to be the head of the family. Not only is he in charge of feeding the family but also all the servants that work under them.
And honestly the dad suffered the most because of his kids. Also we are talking about historical time so her mother wouldn't even dare to openly cheat or find another guy. She was already lucky to be a lawful wife and the dad never had any other lovers either. So yeah I felt bad for him the most.