We had 3 chickens (1 Serama and 2 Silkies) all broody and sitting on one little egg at the same time. That's right, 3 chickens squeezed into 1 small basket. Well, they pushed it out of the nest and it was cold when we found it. We brought it in the house and candled it and it's still alive. My daughter and I decided it would be safer if we kept it in here. Just don't know when it will hatch. Looks like it will be soon.
If I really want my hen(s) to hatch their eggs, I separate them. All the fighting over eggs isn't beneficial to hatching.