It's funny, I had pretty good hatches in my incubators from Christmas day all way till the end of beginning of February before my death bator started causing problems. I would keep the babies separate for about a week, then throw them in the community pen. I JUST now took out the 8 biggest and moved them outside. There is one 7 week old silkie, one 4 week old SF and two BCMs (also 4 weeks old). in that pen, but I have 5 new week to 10 day old babies ready to go in with them this weekend. Silkies seem to be way more mellow than other breeds. They don't pay any attention to the new babies. They just have to be strong enough to handle the stampede of the bigger chicks..
So, the two Silkies that are sharing a LARGE nesting box, both broody, sitting on eggs, I'm hoping they will raise their own babies. It should be fun to watch. I'll try to get photos this weekend. One chicken is facing the back of the box, the other facing the opening. It's like they both want to pretend the other one isn't there.