Initially, the lands where the heart of the Steel Realms are was land where the dragons settled on Helca. An inordinate amount of dragons populated Helca over its existence, going back 1.5 billion years ago when the first dragon flew the cosmic winds to rest on the silent planet.
Family: A three generation collection of Dragons. Families became a thing of the past when humanoids began to arise on Helca. Also, as dragons aged over millions of years, the family unit was too small to protect from large rival clans.
Clan: A collection of families. These were considered too dangerous for the humanoid presence and these large congregations were broken up. Only by tapping in to the Equitas power were wizards able to send dragons in such numbers fleeing into the stars. It happened, though none of the humanoids currently on Helca were responsible. The last were disbanded in the Celestine Age on Helca.
House: This is a formally established bloodline and family, with attendant serants, settlements, and operations which the dragons manage and maneuver against other forces. Most dragons have left Helca, the few remaining ones have organized into Houses – and the vast majority of humanoids are ignorant of this, though those in power watch them closely.
Bloodline: This is just a lineal tracing of the origins of a dragon. Many are loners and are referred to only as “of the Bloodline of ___”.