They'll figure it out. I have a 12yr old 6 lb Min-Pin and a 3yr old 5 lb Manchester and I found a Pit Bull pup approx. 4 or 5 mo.old who is very hyper and wants to romp and wrestle and they are in the process of letting the 40 lb puppy know he is #3 and there are rules to follow Clem has the most seniority and at 6lbs he's the big dog around here -ask him