Are my kitten playing or fighting?

Okay wat disturbs me is you said that about the teeth...they should come in around 4 weeks at the least....That is also a problem about not introducing them...that can lead to fighting and even death. They could of just been playing, but cats don't usually live in packs or with other animals in the wild. They are loners and fight for territory but since they're kittens it could be playing. The older cat is also territorial. You should of introduced them properly because that could damage their relationship. Just let them out with each other when you are in the room and they may calm down a bit.