Yes, sometimes this happens if the 'let down' hormones don't swing into action to produce milk. You'll know if the kittens are hungry because they'll root around looking for milk, be anxious and cry constantly. If she has no milk, you will need to take the kittens from her so they don't starve to death. You can then hand-raise them or pass them on to a rescue organisation. If they haven't had any milk, you'll need to give them Pedialyte before you do anything else. Click here
to learn how.
That link is part of a web site, www.kitten-rescue.com
where you'll find all the information you need about hand-raising kittens.