Intact bitches will fight, especially if they’re of a breed known for same sex aggression. You need to get all three desexed…the bitch he mated with needs to be desexed NOW, before puppies happen.
Also, be prepared to crate the bitches separately. Once bitch fights start, depending on the breed, they may never stop.
Do you know if you are stimulating her correctly? You really need to contact the local humane society or cat rescue for help and instruction on how to properly stimulate the kitten. U should use a warm moist washcloth to rub on belly to stimulate the kitten.