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As most of the French medieval non-royal duchies merged with the throne through the marriage between a independet duchess and the French king or heir to the throne, and the next duke would also be king of France, there wouldn't be any non-royal duchies.
Claude of France, Duchess of Brittany married Francis I of France; the duchy was inherited by their son Francis III, Duke of Brittany and when he died without issue, the duchy went to his younger brother Henry, later king Henry II of France and the Duchy of Brittany merged with the crown.
The title Duke of Aquitaine was held by the English kings after the death of Eleonor of Aquitaine, duchess of Aquitaine in her own right and queen of England, until Aquitaine was annexed by France during the reign of Henry VI of England.
The Duchy of Burgundy merged with the French crown after the death of Philip I, Duke of Burgundy. His mother had married king John II of France and when Philip died at the age of 15 his stepfather "inherited" the duchy.
The Duchy of Normandy was/is held by the English monarchs, but the mainland part of Normandy was confiscated by France in 1204, but queen Elizabeth II is Duchess of Normandy as the Channel Islands was a part of the Duchy of Normandy and still are English.
The Kingdom of Navarre merged with the French crown when king Henry of Navarre became king Henry IV of France in 1589.
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