If you have two day old kittens and they are already infested with fleas, it means both the mother and the area they are living in have a flea problem. Because of this, the only way you can completely kill off the fleas the kittens have is to remove the fleas from both the mother cat, and to find and kill all the fleas that are in the area where they are living.
Instructions
Vacuum up every square inch of your house. When you are done, take the vacuum outside with a trash bag. Because most new vacuums do not use a bag you want to empty it out away from your home. Doing so inside your home may result in some fleas escaping. Place the garbage bag on the curb or in an outside trashcan.
Look for and pick up an insecticide that contains "Insect Growth Regulator." These products are going to kill off the fleas more effectively that insecticides that do not contain the ingredient.
Spray down the entire home, including carpets, rugs, flooring and where your kittens typically sleep.
Create a fresh and clean area for the kittens to play and sleep in. Keep them away from the insecticide and from their old sleeping area.
Keep your kittens indoors. This may have been the origin of the fleas, which means there is going to be more fleas outside. Keep them inside, and at worst, the garage, to protect them from being infested again.
Give your kittens a bath with flea shampoo. Once you have washed one of the cats keep them away until all the other cats and kittens have been washed. You might want to wash them several times.
Keep an eye on the kittens. If you see any more fleas give them another bath. However, if you see more fleas in the home you need to repeat the entire process of vacuuming and spraying.