They can be free ranged and housed together too, if proper introductions are made.
Right at this moment outside, I have 3 year old hens, 1 year old hens, some 5 month olds, some 14 week olds and some 9 week olds, all freeranging together. In just a bit, the 3 year olds will head in to their coop. The younger ones stay out a bit later, but they will all go in their coop together - the 3 year olds are the only ones housed seperately in the original coop.
You just have to hang around a bit when you first introduce them, to make sure all goes well. Some pecking is normal - usually older birds on younger - blood drawing is not.