My chicks have been hatched by the broodies, in the coop, with the flock. When mama hen is ready she kicks them loose. By then they are already a part of the flock and there is no integration issues. They do kind of form mini-flocks. My three oldest chicks, "the chickateers" (3 mo. old cockerels) all hang out together, as do the 5 week old chicks that no longer stay with their mom. But they are all accepted by the flock because they've always been there. Now I have two sets of chicks with their moms, both sets are a week old. Again, accepted as a natural part of the flock.
ETA: My rooster watches over all the chicks. He has a vested interest in their welfare, as they are his offsping (not all biologically, but as far as he's concerned since they are mothered by his hens).