Here's how it works:
* Cats can ovulate multiple times in one estrous cycle. This means a female cat can release eggs on different days, even if she's mated with the same male.
* Sperm can remain viable for several days in a female cat's reproductive tract. If a female cat mates with multiple males during her estrous cycle, the sperm from each male can fertilize different eggs.
This can result in a litter of kittens with different fathers, each with their own unique genetic makeup.
Note: Superfecundation is relatively common in cats, but it's less common in humans.