Some of the clans are recognized by the Empire as legitimate. If these clans take over Katmandu, they are by default the new rulers of the Empire.
Many of these clans do not that the ability to oust the current ruler, the Hansa clan. But they rule fiefs, control commerce or otherwise act in their own business without interference from the Hansa clan. Each clan has origins, goals, directions and characteristics embedded in their culture.
Royal Clan Marriages
There are regional clans in the northlands which make no claim to ruling anything outside their homeland.