Sometimes momma cat senses that there is something wrong with kittens, so she abandons them. Of course, sometimes she gets scared off or injured, so kudos to you if you are willing to take on the task of helping these little ones. If you don’t have experience with kittens, you might want to check with a local rescue group that might have specific advice to help with their particular stage of development. Kittens that aren’t weaned are hard to get to nurse with formula from a bottle, as their eyes are still closed and they go by smell to get to mom’s nipple. Also, without momma cleaning and stimulating them, their eyes may not open on their own, and they can develop infections or go blind. I can recommend a similar tool to the previous advisor, I’ve used a flea comb with great success–it just takes a lot of patience and repetition. A shallow cookie pan with some soapy water placed in front of a low light bulb can draw fleas and drown them, just take care to keep the kittens safe from the water. Fleas can make small kittens anemic in a very short time, but you don’t want to use harsh chemicals on their tender skin. I’ve even used brands that said they were safe to use on kittens, and could still see that it caused them discomfort. Best of luck!