Yes, it happens and more technically is termed "alliance aggression." This goes beyond simply vying for Mom's attention. In fact, the pups usually get along FINE and are best buddies until--their favorite human comes into the room and then all heck breaks loose!
Learn how you can recognize sibling rivalry in your dogs, and manage it. Here's the latest article with tips and information about puppy sibling rivalry.
Image © Amy Shojai, CABC