If a cat is neutered and a cat is not, will there be kittens? - briefly
If both cats are of opposite sexes (one neutered male and one intact female), there can potentially be kittens. However, if both cats are neutered or if they are of the same sex, there will not be any kittens.
If a cat is neutered and a cat is not, will there be kittens? - in detail
The presence of kittens depends on whether both cats have been altered in their reproductive capabilities.
Neutering involves surgically removing a male cat's testicles, which contain the cells that produce sperm and most of the hormones that regulate masculine behavior. After neutering, a male cat is no longer capable of impregnating a female cat because he cannot produce viable sperm. As a result, if one cat has been neutered and the other has not, there will be no kittens unless the neutered cat was previously able to impregnate the unneutered female before the procedure.
Spaying involves surgically removing a female cat's ovaries and usually her uterus as well. This procedure eliminates the cat's ability to become pregnant because it prevents the production of eggs. A spayed female cat cannot conceive or give birth to kittens, regardless of whether she has been with a neutered or an unneutered male cat.
In summary, if one cat is neutered and the other is not, the presence of kittens depends on the gender and reproductive status of each cat. If both cats are female and one is spayed while the other is not, there will be no kittens because the spayed female cannot become pregnant. If one cat is male and neutered, and the other is a fertile female, there will also be no kittens because the neutered male is incapable of impregnating her. Conversely, if one cat is an unneutered male and the other is a fertile female, there is a high probability of kittens being born.