How many sims can you handle at once in a household?

The largest household that I've tried to play had four Sims in it. I failed at being able to keep up with them all. I can handle households with two Sims but even that can get out of control for me. But I'm working on it because playing single Sims, which is what I have always done, can get tedious.

I'm nowhere near being able to add a pet or toddlers yet.