Eight weeks of your kitten's life
After two months, the litter should stop feeding from their mother and be starting to be completely independent with their food. You can move them onto a nutritionally appropriate, energy-dense food that's the right texture and size for them, making sure to do this step-by-step so you don't overwhelm their digestion. You should also talk with your vet about vaccinations at this point.
Your kitten at 12 weeks
All of your kittens will now be growing very quickly. Although their energy requirements have dropped, they still need three times as much energy as an adult cat to help them begin their most intense weight-gain period at four to five months, where they will be growing by 3.5 oz a week. Their sleeping patterns will be more like an adult cat—between 13 to 16 hours each day—and their behavior will be fully socialized so they can play with the rest of the litter and you.
Between 12 to 15 months into their life, your kitten will become an adult cat and reach their full size. By being aware of these different early stages and what they need, you can make sure they reach adulthood healthily and happily.