I have had chicken hens hatch guinea eggs. I do not allow the hen to raise the keets. As soon as they are dry I move them to the brooder. Keets that are raised by or brooded with chicken get imprinted. This causes them to lose the ability to understand that there is a difference between them and chickens.
When the keets mature and start their breeding season, they revert to their instinctive behavior. Other poultry do not understand the races and chases and the attacks from behind with the feather breaking or pulling. This can cause extreme stress to the other poultry.
I raise and house my guineas separately from any other poultry. I can free range them all at the same time in the same area without any incidents. It was a nightmare when I kept the guineas with the other poultry.
The people that get away with keeping the guineas and chickens together usually have very large coops, runs and free range areas. Guineas need much more "personal space" than chickens need.
Guinea keets should be fed a high protein turkey or game bird starter for the first 6 to 8 weeks. I feed mine a 28% turkey or game bird starter. It has the higher levels of protein, lysine, methionine and niacin they need for their proper development.