In The Sims 4, the maximum number of Sims that you can have in a single household is eight. This includes both playable Sims and non-playable Sims (such as pets). However, please note that the base game initially allows a maximum of eight Sims per household, but certain expansions or game updates may introduce features that increase or change this limit.
It's important to consider that managing a large household with many Sims can be more challenging, as it requires more attention to their needs, relationships, and overall gameplay dynamics. However, if you enjoy the dynamic interactions and relationships between a larger group of Sims, you have the flexibility to create and play with up to eight Sims in a household.