German shepards?

Wow, where did you get your German Shepherd? I've only heard of police-trained canines doing that sort of thing. That aside, German Shepherds are herding animals, and they can get nippy when they're trying to herd you if you get difficult. Though usually it's nipping at the ankles, not at an arm.

Dogs dont have hands so use their mouths to grab for things. If someone has hit her or mistreated her using their hand sh will automatically use her mouth to defend herself. You must stop that ridht away. Use a chocker collar and when she goes for someones arm yank very hard and sharp with the leash attaced to the collar and yell if a very loud angry voice no. She will associate her acction with the choke on the collar and your angry voice and the word no. It may take a few times. When she sits back and listens give her lots of praise and rubbing in a very happy voice. Do not reward with treats. You want her to respond to the tones in her voice.

Well, be a parent to him. If he bit, I think its not bad to spank him a lil. Just like parents teaching their children not to that because its bad.:)