I also posted this in your other thread -
Firstly, ignore anyone spouting the 'alpha' and 'dominance' bollocks. Cesar Milan is WRONG on those things. The research on wolf packs which led to all that thinking was completely flawed as it studied a captive wolf pack, not a wild pack and the behaviour was totally different.
And anyway, dogs are not wolves. They are dogs.
How old was the puppy when they got it? Where did they get it from? If they got it from a puppy farm then the pup may not have been with its mother long enough to learn bite inhibition. Tell your friends to Google it and use the 'yelp and shun' method. It really works.
Plus the dog sounds to be bout 1 year old? This means it's entering a 'teenage' phase and is going to be naughty! Has it been neutered yet? That could make a big difference in calming him down.
Ultimately they need to go to dog training so they can learn to be better dog people.