I have had hens raise batch after batch of (bantam) EE/OEGB/Cochin mix chicks. Never did have a problem with mine being picked on by other hens. Mine did have the opportunity to free range. I had Roos (a pair of Self Blue D'Uccles) that took on raising some orphaned chicks (mom died shortly after she hatched them). The babies would snuggle up under the roos' wings.