Amjoie, I have been able to have 10 (with pets) since I bought Pets. I was surprised when the game let me go over the 8 limit. I tested it out and I definitely can't go over 8. If I have 6 pets (like to get the unicorn to join) I can only have 4 people sims, but if I have 4 then the unicorn can't join my household.
My current legacy family has 7 people and 3 pets. I am not having any issues with them, except with the IFs aging up. Though come to think of it, it was only when two were aging up (with twins). I assumed it was a conflict with SP, OW, or ET but maybe it is related to this idea somehow? I really don't know what to think.
