Two Kitties In A Basket

A litter of kittens usually consists of two to five kittens. They are born after a gestation that lasts between 64–67 days, with an average length of 66 days. Kittens emerge in a sac called the amnion which is bitten off and eaten by the mother cat.
For the first several weeks, kittens are unable to urinate or defecate without being stimulated by their mother. They are also unable to regulate their body temperature for the first three weeks, so kittens born in temperatures less than 27°C (80 °F) can die from exposure if they are not kept warm by their mother.
The mother's milk is very important for the kittens' nutrition and proper growth. This milk transfers antibodies to the kittens, which helps protect them against infectious disease. Newborn kittens are also unable to produce concentrated urine, and so have a very high requirement for fluids.
Kittens open their eyes about seven to ten days following birth. At first, the retina is poorly-developed and vision is poor. Kittens are not able to see as well as adult cats until about ten weeks after birth.