Aggressive Male

Question
We have two 9 week old Aussies, Littermates. Our male is gradually becoming more aggressive both to us and his sister. We have read very many books about training a single puppy and they don't talk about what to do when you have two to train. We would like to know what is 'normal' and acceptable and what is not. What is the difference between play and fighting and how can we easily nip this in the bud? Thank you.

Answer
Most breeders would not sell litter mates to the same owner, which is why you don't see many references to raising two pups together.  While it can be done, it takes some real effort.  Your puppies, after all, speak "canine" and would rather talk to one another than you.  Just as if you and your sister or brother were suddenly dropped in Beijing and no one spoke English but your sibling - wouldn't you be looking to one another for conversation?  So, the real secret to training litter mates is to train them separately.  Take each pup to a different puppy class.  When at home, train one while the other is contained in a different area and vice versa.  Make sure that they get to socialize with other puppies WITHOUT their sibling, and do it often all the way from puppy hood until they are adults, even if you have to take each one to a day care once per week.  This is not easy;-)  But, it's possible.  
To determine if the play is normal, gently pull the "aggressive" puppy away from the "underdog" - if the underdog goes back to the other pup, it's probably ok.  If she hides or tries to get away, they should be separated.  Nipping, growling and wrestling are normal.  Biting that punctures, one pup rolling the other, and posturing over a pup not letting it up within a normal amount of time,  Soft, curved body posture, with lots of play bows, happy face (open mouth, tongue hanging out, squinty eyes) and parallel running are all normal.  To see normal play, check out this youtube of my dog and one of her friends:
http://www.youtube.com/watch?v=YJKWji4R544

You are probably making a wise decision, based on your family situation.  I hope you find the little one a home where the family will socialize him well (they need to see lots and lots of other puppies and new people every day) and where he can get the exercise and training he needs.  Meanwhile, for the remaining pup that you will keep, this breed needs extensive socialization, but is very smart and biddable (easy to train).  Please do take a class anyway, with a positive trainer who has experience with the breed.  You won't be sorry.  Someone once said, "I asked God for a friend - he sent me an Australian Shepherd"  These are loyal, affectionate dogs, and can do many tasks, but are not great family pets if they are under-socialized or left to their own devices.  They need a job, but the job can be obedience, agility, freestyle, frisbee, and other fun things!