He is a puppy - of course he is treating everything like a chew toy! I wouldn't say he is "mean" or "aggressive" - it just sounds like he is exhibiting normal puppy behavior. Make sure he is getting enough exercise/mental stimulation and absolutely enroll him in puppy training classes if you haven't already. The whole family should be involved in his training, especially the kids so they understand how to safely interact with the dog. Owning a rottie is a privilege and a responsibility.. I have found that training with the help of a professional is not optional (especially as a first-time rottie owner).