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The Bloodroyal is an ancient title traditionally held by the head of House Yronwood. Prior to Nymeria's War, the Yronwoods were rulers of an independent kingdom in Dorne, styling themselves High Kings of Dorne, among many other titles.
When the Yronwoods bent the knee to House Martell, they were allowed to keep their title of the Bloodroyal.
- The World of Ice & Fire, Kingdoms of the First Men.