A royal family is the immediate family of kings/queens, emirs/emiras, sultans/sultanas, or raja/rani and sometimes their extended family.
The Royal Family of France in classical costume during the reign of Louis XIV.
Emperor Pedro II of Brazil and other members of the Brazilian imperial family in Rio de Janeiro, 1887
Duke is a male title either of a monarch ruling over a duchy, or of a member of royalty, or nobility. As rulers, dukes are ranked below emperors, kings, grand princes, grand dukes, and sovereign princes. As royalty or nobility, they are ranked below princes and grand dukes. The title comes from French duc, itself from the Latin dux, 'leader', a term used in republican Rome to refer to a military commander without an official rank, and later coming to mean the leading military commander of a province. In most countries, the word duchess is the female equivalent.
A portrait of James Brydges, 1st Duke of Chandos wearing the robes of the British peerage.
In the 1260s Birger Jarl bore a ducal coronet and used the Latin title of Dux Sweorum (Latin for "Duke of the Swedes"); the design of his coronet combined those used by continental European and English dukes.
Bishop Benedict (1254–1291), a son of Princess Ingeborg of Sweden and Birger Jarl, was the first Duke of Finland
