....That's not an EA thing because in one of my files, I had twins when there were seven sims in the household and with them born, I was bumped up to nine sims, and no pets. Or I just magically glitched it into accepting nine sims.....somehow.
It could have very well been a glitch or a mod because EA code specifically says up to 8 Sims, up to 6 pets, up to 10 per household. My entire dynasty has had 8 people in it for the most part and I was never able to increase that size other than the 2 pets.
Also without help from a mod, the game doesn't know how to process more than 8 portraits for Sims on the left hand side. So even if you did have that many you still would have only been able to control 8 unless you also had a mod to see more portraits.
Oh, it's crazy towards the end. Way back when with the Man Dynasty during the last couple generations I would sit sometimes for 5 minutes for the file to load.
And this is the bonus of having a "Man house". Juxt says her dynasty was taking up to 2 hours in Bridgeport towards the end and the Grims haven't loaded in under 15 minutes since Generation 5 was born. I think the only reason it's still so low is because I just demolished their house.