I’m only in my sixth year of keeping chickens, all hatchery stock females in enclosed run except for supervised free range time, however. I also keep a mixed breed flock and have only had a couple repeat breeds. So far, mine tend to group more by age.Is it a matter of looking alike, or is it a matter of being raised together? I think it's fairly common for the same-appearance ones to also be same-breed, same-age, and raised together. It could be hard to sort out which of those points is actually more important to the chickens.
If someone got 1 each of several breeds, the same mix each year, I wonder if they would tend to stick with their yearmates or their breedmates. (If someone's flock does have this composition, I'd be quite interested in knowing how they interact.)
I also wonder if chicks raised by a hen might want to hang out with chickens that look like that hen, regardless of whether she was their biological mother or just raised them.