My 2 chocolate keep fighting with eachother!!!!?

I have 2 chocolate lab's a female that's 14 months old and a male that's 5 months old. They are alway play fighting with eachother but they get ruff I'm scared that one or both of them are going to get hurt, since they bite eachother faces, I tell them no and separate them but they keep doing it?? Any ideas on how to get them to stop?? Any ideas would be greatly appreciated!!!