One litter of kittens can have multiple “father” cats.

I've often wondered how a litter of kittens look so strikingly different from each other. Perhaps this is the reason? I never knew this!

Because female cats release multiple eggs when they are in heat, they can become pregnant with kittens from more than one “father” cat at the same time!

https://www.dogdoors.com/questions/why-do-kittens-from-the-same-litter-look-so-different/