2 Puppies & possessiveness

Question
We have 2 male (fixed) lab/german shepherd mix puppies approx. 6 months old.  They are brothers and we rescued them about a month ago from a shelter.  At times, one of the puppies gets very possessive over me when the other puppy comes around.  He growls at his brother or snaps at him.  Doesn't bite him but is more aggressive than his "playing" usually is.  It happens sporadically & they stop when we reprimand them but I want to break this behavior while they are young so it doesn't escalate into something more, especially with a small child in the house.  The only other time there are any "issues" with them is sometimes when they are playing with a toy, one will get a little more possessive or with a "special" treat.  The possessiveness is never against us or my son, only with each other.  Again, they stop as soon as we reprimand them but I would like to try to totally stop this behavior, if we can. By the way, they are in a basic training course with the plan to continue them into the advanced/good citizen class.  Our trainer suggested to basically reprimand strongly with big movements to stop them/distract them & this works but I would like to just stop it from starting.  Any other suggestions you could provide to help curb this behavior would be appreciated.

Answer
Well so far you are doing what I would suggest.  Also give them treats separately so they do not have a reason to fight.  It is a completely normal behavior and most likely will diminish as they establish pack order.  Just be sure to keep yourself at the top of it!