I dunno about in sims 3, because i haven't heard much about it but if you use cheats in sims 2 you can have as many people in the household as you want. for example one of my family's has around 15 sims in it i think. So im guessing sims 3 won't be any different.

Ive tried but you cant.. so yeah there might be a cheat :D

I think, pretty sure, that you can only have 8 people in a household, cus i have tried to create more but it wont let me