Again, fisherlady would have more ideas as she keeps her roosters in with the hens and chicks, but they should be fine if the rooster is docile and the rest of the flock is not too inquisitive or aggressive. I think it sounds like you could try it, just watch.The sisters do get along and the roo is docile and doesn't bother with the girls. Both hens seem comfortable in their present setting. Just wondering about the chick's when they hatch.
Be aware that little chicks are very, very, good at getting themselves into fixes...ie squeezing through small holes in fences, falling into bowls of water and drowning, so you may want to chick proof your yard if you free range....especially keep a close eye out for predators as the sound of chicks peeping draw them out.
Lady of McCamley