I have 3 broody hens sitting on 40 or so eggs. 2 speckled Sussex and a buff Orpington. However....as the eggs have started hatching, the buff seems to be very aggressive towards the hatchlings. She's already killed one and wounded another (s/he is on the mend!) Is it normal for a hen to want to kill its young? I find it odd, especially since she is the broodiest out of the 3. I'd separate her, but the Sussex's are on the smaller side and need the buff to cover up the rest of the eggs they can't cover. I've been very consistent in checking for hatching eggs and already hatched chicks to ensure the buff doesn't kill or wound any more chicks.
If the sussexs are more maternal, I'd give the hatched chicks to one of these hens separated from the others. If possible give each hen her own nest with the appropriate number of eggs and/or chicks. This could end your problem. Should the orpington continue with her behavior give all the chicks to the sussex hens. Quite likely these two hens would team up and raise their chicks together.