agressive 2 yr old female German shepherd

Question
I have a 2 year old female German shepherd that has been spayed. The people that had her before we adopted her had her in a cage all the time she never had any contact with people at all until we got her. Shes fine with us and our 10 month old Female Pit Bull but when my half brother or my cousins come over her hair stands up and she starts barking at them. We have tried pinches on the side, proving our dominance over her, and obedience school. Can you please help us stop this aggression towards other people.

Answer
Cut out the pinches.  If you were taught that in obedience school, no wonder you are having problems.  You need to find a book with modern, more  positive methods.  Try some of these:

Here is a list put together by the professionals at a dog guide school for those caring for their dogs.

The Cultural Clash by Jean Donaldson, 1996

Excel-crated Learning by Pamela Reid, 1996

Don't Shoot the Dog, by Karen Pryor, 1996

Surviving Your Dog's Adolescence, by Carol Lea Benjamin, 1993

Second Hand dog, by Carol Lea Benjamin, 1988

Dog Problems, by Carol Lea Benjamin, 1989

Super Puppy, by Peter J. Vollmer, 1988

HELP, Mt dog Has an Attitude, by Gwen Bohnenkamp, 1994

Owners' Guide Better Behavior in Dogs and Cats, by William Campbell, 1989

What All Good dogs Should Know, By Wendy Vollmer, 1991

How to Raise a Dog When Nobody is Home, Jerry Kilmer, 1991

Through Otis' Eyes-Lessons from a Guide Dog Puppy, by Patricia Berlin Kennedy and Robert Christie, 1998

Puppy Primer, by Brenda K Skidmore and Patricia B. McConnell, Ph.D., 1996

Beginning Family Dog Training, by Patricia B. McConnell, Ph.D., 1996

Try having your frequent visitors show up with a treat for her.  It may not be quite as effective with  Shepherds  than with more food motivated breeds.  Your behavior is important to.  Control your emotions.  If strangers cause you stress, it will only confirm that she should fear them.  Don't coddle her either, that rewards her for showing fear and hostility.  Punishment by pinching her or something else adds to the problem.  

Instead, greet them warmly, letting her know how glad you are to see them.  You, the leader are happy to see them, they have a treat for her, and you aren't reinforcing her fear.  At 2 years old, you aren't going to see an immediate change.  I encourage people to adopt,  and hate to see problems due to past baggage.  Quite often it stems from the important 6-12 week period when puppies are the quickest to accept new things.  Excessive use of the crate creates problems.  One, or at least her private enclosed space might help too.  A large plastic crate, perhaps even with the door off, would give her the comfort of knowing she could always retreat to it if the strangers were too bad.   I would never shut her in it when you were around.  You could even start with a large cardboard box and see if she liked it.