It starts to get a bit awkward how much Steve Martin loves his daughter and doesn't care about his son.

He's such a soppy git about her it's almost sickening, and throughout this sequel, it becomes a bit of a joke about where his male kid is.

Story continues... "Matty's staying at a friend's"
Story continues... "Matty's out for the day."
etc.

Even in the first film, it was somewhat similar. Matty asked about how to walk down the aisle, Steve Martin showed him for six seconds and then sent him to bed so he could get soppy about his daughter again.

Matty is apparently just always in the way of the story, so they shove him off out of the way at every opportunity. Everything is all about the women in his life, and Matty may as well just go f himself, honestly.

Watch it again and pay attention to where Matty is. Gives a whole new perspective.