Technically, probably about twenty-two but that would only be if I included the feral cats. When I was younger, my mom rented a country house that had cats that had been there since the owner's grandma had lived there. They weren't the kind of cats that would let you pet them, but they would accept food if you left it out for them. So even though the owner said we didn't have to, we fed them, especially in the winter. Toward the end our of time there, they would steal food straight from my fingers but dodge just out of my reach to eat the food. Stingy brats, but there was probably about twenty of them, but I'm not sure. Then we had two indoor cats that I got as a present from my Grandma. So that would make it about twenty-two cats.
But if you consider the cats we actually took care of the most we had in our direct care was three. My grandma's mom cat had a litter of kittens but they were getting eaten by something so my mom offered to nurse them until they got bigger. My cat Midnight, thought they were annoying and would paw them away when they wanted comfort. So my mom temporarily took care of them for a couple months and my cat Midnight taught them how to hunt in the backyard. When they were big enough, we returned them.