Besides that, If I'm not mistaken after the father and mother start the discussion over the divorce the dad pretty much goes straightforward towards the daughters room, then the next day spends it with her and finally the third day remembers he has a son and decides to look for him. I'm not saying the son has a stellar performance for son of the year, but he basically "can" try to see the reactions of other family members due to the possible divorce (even searching for the dad in guest room), just as well as the dad can do it but him (dad), doesn't try to check on his son until the third day and completely voids the son from interacting with him (since before events of the game apparently), so it is no surprise that the son doesn't actually wish to speak to the dad and speaks badly of him, plus the only time I remember the son being openly an ass towards the dad was on the second or third day when he ignores the request of the father to speak by saying sorry and leaves because he "needs" to check on his cousin situation.
Just so everyone knows, here's a direct quote on the father/son dynamic from the author itself in reply to another user in a different forum: Will it be possible to improve the relationship between father and son? I want to be a real dad for my junior.
Ah, unfortunately not. I'm afraid that there won't be any saving Junior from his blind bitterness towards his father, mostly due to their vast contrast in character. Plus, he's pretty much your average teenage shithead.