I think it most likely dose not happen when your not there & if I am right about that it's over who owns you & who get what attention.
You need to watch your not favouring either dog in anyway. I would not encourage an alpha dog(by fave older dog as you where) in your situation as there is no such dog fit to take the role. Play it straight down the line with everything fair & equel.
In your situtation I would remove myself everytime they started & you'd be surpriced to see that most likely they stop to follow you. Meaning it is not really serous & more about having your attention & affection & who gets it.
Dogs make everyday life enjoyable...........