This is literally the scenario in the Age of Worms campaign where the Big Bad's second in command is a dracolich.
Various The World Of Darkness games give vampires and mages the ability to create what effectively is their own Dragon. Vampires in both Vampire The Requiem and Vampire The Masquerade have ghouls, human slaves who are addicted to vampire blood, inherit a share of the vampire's powers, and generally acts as a vampire's bodyguard and enforcer wherever the vampire him or herself isn't required. Mage The Awakening gives mages have their own version of this, called Sleepwalkers. These are humans immune to paradox, that allow mages to do all sorts of nifty, reality bending tricks without a nasty abyssal horror eating their faces off.
In the Dungeons and Dragons cosmology, Dagon serves as The Dragon for Demogorgon, he closest thing the Demons have to a leader.
Also in the Dungeons and Dragons cosmology, Tiamat (the evil Dragon Goddess of the chromatic dragons) has five dragons (one of each chromatic type) as her Dragons.
