The Queen can choose from five titles for a man duke, marquess, earl, viscount or baron and for a woman duchess, marchioness, countess, viscountess and baroness. Dukedom is the highest of all five.
Typically, family members are given the titles of Duke and Duchess, but the Queen can choose to bestow more than one title. ive several.
In the case of Prince Harry's brother, Prince William, he and his wife, Kate Middleton, became the Duke and Duchess of Cambridge, but the Queen also granted Prince William the titles of Earl of Strathearn and Baron Carrickfergus.
Prince Charles, Harry and William's father is the Duke of Cornwall, and the Queen's second son, Prince Andrew, was given the title Duke of York.
But breaking with tradition was the Queen's youngest son, Prince Edward, who chose the title Earl of Wessex when he married.