It’s never too early to begin training your puppy
By far the most important early training for any puppy is socialization to other puppies and dogs, to people and to everything else they will ever encounter in their lives. This is also the ideal period for a puppy to “learn to learn” and that command compliance might earn a reward.
Littermate syndrome is a risk when raising sibling puppies
Some sibling puppies raised in the same household develop behavioral problems because their deep bond impedes comprehension of human and canine social cues, interfering with social development and communication skills.