Hi Chuck,
Congrats on the baby kittens! It’s hard to say without knowing the age of the kittens as well as what kind of environment and interactions they are having. Could the aggression be mistaken for play? Is there competition for food or attention from mom (this may be more attention seeking behaviour)? It would be reasonable to have an examination done to make sure there are no internal problems that are not visible to you at home.
I hope this helps.
Dr. Ryan Llera