We've had babies since 6 weeks old and after the initial quarantine (they came from the same breeder as my older girls) they've been in a temp coop next to my big girls. This week we started letting them free range together but sleep apart and yesterday they went into the big coop together. No problems. Tonight they're all cuddling and roosting together. There's been a few pecks and chasing and whatnot but nothing too major. I'm relieved.