Three of the eleven Dukes of York either did not marry or had already assumed the throne prior to marriage, while two of the Dukes married twice; therefore, there have been only ten Duchesses of York.
The ten Duchesses of York (and the dates the individuals held that title): In 1791, Princess Frederica Charlotte of Prussia (1791–1820) married Prince Frederick, Duke of York and Albany (second son of King George III); she thus became HRH The Duchess of York and Albany.
Her husband held one double dukedom (of York and Albany) rather than two.
The Duchess received a warm welcome to Great Britain but following a troubled relationship with her husband, the couple separated.
The two previous dukes of York and Albany had never married; since her husband was the last duke of York and Albany, Frederica was the only duchess with that double title.