I don't know if it makes you feel any better but any body that has more than one dog under one roof finds the play time can be relentless at times! I have two boy yorkies. One is about a 3/4 lb bigger than the other. One week Chief is the alpha dog. The next week Harley is the alpha even though he is the smaller one. They are never aggressive with each other unless a bully stick is involved! But, they do play fight non-stop if they are awake. Hopefully they will stick to play fighting...
