:joy: I have noticed an increase in random mean interactions since Parenthood, too. Though, I haven't seen a fist fight yet.
The siblings of my current household (maxed relationship) have recently been attempting to start arguments with one another. I think it's supposed to be a new way to introduce random acts of sibling rivalry, but I'm not sure. The instigator was always the older sibling while she was Confident. Was your sim confident? In general, it seems like most sims pull more mischief and mean socials while they're in this mood.