Well, that's the thing, they were all raised together! The roo is about a week younger than the WR though. I also have 3 NHR that are the exact same age as the WR and were raised together, and the WR won't have anything to do with them either. YET, I have 3 DeKalb amber links (WE THINK!) that are white, with a bit of reddish tan markings around their necks, and more of a cream white than the solid, bright white of my WR. These 3 are my youngest ones, and about 5-6 weeks younger than the WR, and they are accepted into the WR flock. NONE of the other chickens are accepted to even scratch in the same area as the WR. The WR hens will chase them away, and peck them! The WR are 16 weeks old, and HUGE! They look like they'll start laying at any time.
Oh, and some of the younger chicks allow the roo to mount them, but not the WR, and not 3 cream colored that hang with the WR. They chase that roo all over the yard, and will pull his tail feathers!