Yes they can!! Female cats mate with many different toms in the same heat cycle and they ovulate new eggs each time. This leads to superfecudation: one pregnancy from more than one mating.
What is interesting is that you can actually detect superfecudation by examing the kittens in a litter.
It is possible to calculate the date of a kittens conception (within a day or two) from the date when the first adult teeth come in. So if two litter mates start losing their baby teeth on different days then there is a decent chance they have different fathers.
So for example if you have two kittens that are brown tabby and two that are tortoiseshell from the same litter, than the mother has mated with more than one cat.