I have gotten two puppies one for my mom and dad (Lady) and one for my family and myself (Winny), both from the same litter. Well I brought my pup to my parents house to visit her sister and all was good they were play fighting but seemed to be having fun. And then all of the sudden they growled and Lady bite and drew blood from Winny. Of course I broke it up immediately but I am not sure how to fix this problem? Winny is much bigger and Lady was the runt of the litter. They are 8 week old mutts as far as any training Winny can sit and stay come when called I have her nipping down to a minimum and her walks are improving, she still uses puppy pads but has started going out side as well. Lady can sit, go lay down, her nipping has gotten better but still on the high side and she walks good, she uses puppy pads and she is a ball of energy. I think it was it was playing that got out of hand my wife thinks that Lady dose not like the fact that Winny is much stronger, either way I can't have them behaving like that Please ANY IDEAS?