Are they yelping when they play? I raised 2 litter mates together a couple years ago (they are now 2 1/2 years old and live in separate states) that were mine and my daughters puppies. They would play so rough. They would be running at full speed and grab each other by the tail and pull each other to the ground. They would really play rough but unless there is yelping (which tells the other they are too rough) I would not be concerned. I just brought home a new Yorkie and while my 2 1/2 year old and 12 year old were playing she got near them and she bit the 12 year old and he yelped. Since then the 2 1/2 year old has taught her how to "play" and now she will jump in and play with them with no yelping.
They will let the other know if they are being too rough by yelping. Otherwise it can sound pretty intense but they are having fun.
Good luck and enjoy them when they are this little.
__________________  It's raining Yorkies here! LOL Teek  ,Rowan  , Raksha (Grand Puppy)  , Raelyn  |