Aside from not getting enough exercise as others have already mentioned, I have to say I've seen this same situation more times than I can count. People who don't like or understand dogs often expect them to respond to speech, because they don't care enough to learn the specific commands the dog knows, or they say a command to the dog without conviction, and don't follow through; or they use different words for that thing they want - since the dog didn't listen last time. in all of these cases a dog, and especially a GSD, will learn very quickly not to listen to that person. This is why a lot of trainers say that 85-90% of dog training is really people training! Your family can be left alone if they want, but your puppy needs to (a) learn a "leave it" or "go away" or "place" or something which fits what your family is trying to tell the dog, and (b) they have to say the correct word EVERY TIME, say it with conviction, and follow through for a bit by showing the dog what to do. Without those steps your dog is going to continue to get worse about listening to them. And honestly, without more playtime and exercise, who can blame that poor puppy from wanting to play every chance it gets!
It's not the size of the dog in the fight, it's the size of the fight in the dog. Mark Twain