We've had hens 'sharing' eggs and chicks several times and they've all grown up successfully, seeming to relate to both mums. In fact, last year, we had one chick with three mums and they all looked after it with no fighting! Keep an eye on the chick, but it can survive two to three days after hatching without food. Just ensure that you keep some chick crumbs, some small grit and water nearby so that it can reach them easily when it needs to feed and drink. Good luck - hope they're all reared successfully. Keep us posted! Janet