Is AUTHOR wrong in the post ? POST : TL;DR: SO doesn’t want to do any sort of day-after wedding brunch. My parents want to host a smaller one for some people on my side, which I want us to attend. AITA for insisting on it?

Background: SO and I are getting married this summer. My parents said they’d like to host a day-after wedding brunch for us that included our families and OOT guests. I thought it would be nice, SO didn’t, and an argument ensued. Background is that my parents have definitely not been the easiest people to work with, even with the rehearsal dinner or any other planning, or clearly supportive of our relationship in general. I thought this was a nice gesture, but SO recognized it as sort of a sign of wanting more control, and also just doesn’t want a brunch for a number of reasons (it would be a big to do, things planned by my parents tend to be kind of chaotic and unorganized, and the somewhat complicated background relationship with my parents, and SO just wants us to be alone that day). Anyway, I eventually came to my senses, especially given that this brunch would entail a lot of people and would really be too much, and I told my parents that we were declining their offer for this day-after brunch.

More recently, my parents said they’d like to have a brunch for a smaller subset of people being just my parents, my siblings and their families, my father’s side OOT guests (my mother won’t have any there), and _maybe_ grandparents. Roughly 18-20 people.

I talked with SO again about this, and another sort of argument ensued. I continued talking about how I thought it would be nice both for us and anyone attending, and that it seems like a small thing that would mean a lot to other people (especially with the day after being Father’s Day, I guess - it seems to mean a lot to my parents and would to the OOT guests that’d attend). SO doesn’t want to do it for the same reasons listed above, and also said they’d feel weird doing something with my side and not their side (even though they didn’t want a brunch with everyone, and said they wouldn’t want to go to an additional thing with their family). 

Anyway, I’m having a hard time not feeling like SO is being selfish and stubborn and that we should do this.

AITA for still thinking we should do this brunch, and not letting it go? 