My newborn kittens are different sizes. Is the small one getting enough milk?

The best thing you can do is to weigh her twice daily to make sure she's growing appropriately. Kittens should gain 10% of their birth weight per week, or if you don't know the birth weight you should make sure the kitten is gaining weight each day and not losing weight. If she is not gaining weight it would be a good idea to see a vet for an exam and potentially to supplement with bottle feeding.

If by fighting you mean they are pushing each other out of the way this is normal behavior. A cat has 8 mammary glands so there should be enough room for everyone but sometimes the mother doesn’t make enough milk. The best way to determine whether or not the kittens are getting enough milk is to weigh them each daily using a gram scale. They should gain about 100 grams per week and should be gaining every day.

Even though Cleo's nipples don't feel like they have milk, there will be milk present. I would weigh the kittens daily. Gaining 1/4 to half an ounce daily until they are weaned is considered healthy. Healthy kittens weight between 2.8-6 ounces when they are born. If you notice the kittens aren't gaining weight, then you may have to bottle feed them with kitten formula such as KMR to make sure they get enough nutrition.

The best way to determine if your cat is producing milk is by observing the kittens. Newborns spend long hours nursing - up to 8 hours per day - with sessions lasting up to 45 minutes. When the mother's milk is being let down, the kittens will each latch onto a preferred nipple and stay there. If you observe closely you will be able to see their little mouths and tongues moving from the suckling action. Often their ears may move as well. Nursing kittens will knead the mother's abdomen which is an important stimulus to milk let down. After a feeding session, the kittens will have round, full bellies and will fall asleep. Ideally, healthy kittens who are nursing well will gain 7-10 grams every day. They can, and should, be weighed every few days to confirm gains.

As long as they are all continuing to gain weight steadily you can continue to monitor them for now. It is normal to see some variation among littermates. However if they're smaller kittens show other signs are not thriving such as decreased play behavior, being isolated from the other kittens, or they stop gaining weight then you need to try to supplement formula again.

He is not so far away from his normal weight,, actually. Count 100g/per week. So if he is a week old and weighs 90 g, that would still be ok, especially since he may not have been fed for a day before you found him. Keep feeding him kitten milk (pet-lac), as much as he wants, and keep him warm. Do not forget to stimulate his genitals and anus after feeding so he urinates and defecates and keep him clean (use a moist warm paper towel or tissue to rub gently, like a mother cat's tongue). If he is healthy, ie does not have any congenital conditions, he should grow normally. If you have any other cats in the household, it might be a good idea to let them interact with him, you might actually find a mama that way who may not have milk, but takes on the hygiene and babysitting and eventually teaching him to be a cat! It is very rewarding to raise a kitten! Enjoy!

You should be weighing them every day or two to make sure they are gaining weight. If the little on is not gaining weight then you will know it is a problem and you will need to get it to a vet. You can use a kitchen gram scale to weigh them.