The Dragonborn Clans are presumably scattered independent groups of dragonborn. Little is known of them.
The Clans are mysterious, and little is currently known of them. It can be presumed they are spread throughout the world beyond Erilán.
The only known Clan is the Fireblus Clan, who live on an isolated island off the Crimson Coast, where they often raid. They are believed to main consist of red dragonborn, though other similar colors are present within their ranks. They are associated with being heated and angry in their nature.
It can be presumed there are many other clans, who likely consist of several dragonborn of similar types.