Queen Elizabeth II's health condition, which recently forced her to cancel several planned events for Christmas, has given rise to speculation about who will be the next queen. Rumors have circulated for years that the 90-year-old queen is debating stepping down as the world's longest serving monarch.

Amid concerns about the queen's health, the question raised is if Kate Middleton will sit on the throne next. Despite several rumors over the last few months that Middleton and Prince William may completely take up the royal duties, it is unlikely that the Duchess of Cambridge will be crowned the next queen.

In case the queen gives up her throne, retires or dies, the next in line to sit on the throne will be Prince Charles, the eldest son. Prince Charles has the title of Prince of Wales and is also known as Duke of Rothesay and the Duke of Cornwall. However, this will not make his wife, Camilla, the queen, after their extramarital affair when he was married to the popular late Princess Diana.

Charles' oldest son, Prince William, would then become the new Prince of Wales and the heir to the throne. His oldest child, George Alexander Louis, is now third in line to the British throne. Princess Charlotte, the daughter of Middleton and Prince William is fourth in line to the throne.

In Britain, the crown is normally passed from the monarch to the eldest son. As King George VI had no son, the crown passed to his elder daughter, Queen Elizabeth II. However, in 2011, the Act of Settlement was changed before Prince George’s birth, to ensure succession would not be affected by gender of the child.