As a female-line granddaughter of the British monarch, Alexandra was not entitled to the title of "Princess", nor to the style of "Her Royal Highness". Instead she was styled Lady Alexandra Duff, as the daughter of a duke, even though she was born fifth in the line of succession to the British throne. Alexandra and her sister were unique among British princesses in that they were descended from both William IV (through his mistress, Dorothea Jordan), and William IV's niece, Queen Victoria, who succeeded him because he left no legitimate issue.