CAT had litter of "1" how rare is this?

actually happened 2 1/2 years ago.

had a cat that had one kitten and we still have both today. the kitten,now a 2 1/2 years old CAT,has developed to be physically smaller in size for a grown-up cat for her age,despite being well fed. however despite the cat being extremely,extremely intelligent,it still behaves like a kitten.

my question,how rare is it for a cat to have just one kitten? a vet had mentioned the cat might have had stillboens that we didnt know about,however
we lived in a one room studio apt therefore if the cat had more than one kitten(stillborn)we likely would have known.

so anyone know how rare a cat having one kittern is? any comments about how that one kitten(a cat today)has developed from what i wrote in the second paragraph?

thanks

CAT got pregnant by a male that had been an incomplete neuter. This would cause a very low sperm count, therefore, a small litter of one. The small size of the kitten could be from worms, so even if it eats all the time it isn't getting the nutrition it needs. The quality of the food would also have to be checked for nutritional content. As for intelegence..that is due to the exceptional amount of attention given by the owner. The more you interact with the kitten the more it learns.
Oh, and this is gross, cats eat their stillborn young. So if the kittens were born during the night and there was only one kitten in the morning?...

about the male cat being an incomplete neuter,do you mean the male cat was not completely fixed? just so happened,one of the two vets in the area had a series of cat owners complain thier female cat got pregnant AFTER having the cat "fixed" at his office. my sister in law was one of the cat owners and it was so funny.

yes,the cat of one litter has received extreme amounts of attention from the second she was born and "spoiled rotten" so to speak.

i assumed the petite size of the cat might be generically related to the fact she was a litter of one(maybe the mother cat was sick).