This combination of photos shows, from left, Princess Margaret Rose feeding a biscuit to a Pembrokeshire Corgi held by Princess Elizabeth on July 5, 1936, Princess Elizabeth and Princess Margaret Rose on June 7, 1938, and Princess Margaret Rose and Princess Elizabeth at the International Horse Show in London on June 21, 1939. The princesses often dressed alike as children and into their teens. (Source: AP Photo)
Britain's King George VI and Queen Elizabeth appear with their daughters Princess Elizabeth, left and Princess Margaret, on the balcony of Buckingham Palace, London, June 22, 1939. The princesses often dressed alike until their teens. (Source: AP Photo, File)
Queen Elizabeth II shakes hands with actor Charlie Chaplin at the Empire Theatre in London on Oct. 27, 1952 for Royal Film Show, a benefit performance to aid the Cinematograph Trade Benevolent Fund. (Source: AP Photo, File)
Princess Elizabeth, 16, center, appears with her mother, Queen Elizabeth, and her younger sister, Princess Margaret Rose, as they walk to the parade ground of Windsor Castle for a review of the Grenadier Guards on May 19, 1942 in Windsor. Queen Elizabeth II's style has been hyper-documented since her birth, young princess days, ascension to the throne and now, more than 70 years into her reign.(Source: AP Photo, File)
Britain's Princess Elizabeth talks to an ambulance officer at a stand-down parade at Buckingham Palace in London, on Oct. 24, 1945. (Source: AP Photo, File)
Princess Elizabeth, 14, right, appears with her sister Princess Margaret before giving her first radio broadcast in London on Oct. 13, 1940. (Source: AP Photo, File)
Queen Elizabeth II appears with her husband, Prince Philip, Duke of Edinburgh, at the Empire Theatre in London for the world premiere of the film "Dunkirk," on March 20, 1958. (Source: AP Photo, File)
Princess Elizabeth wears a new style of hat during a visit to the Yugo-Slav exhibition at Burlington House on Jan. 31, 1944 in London. Her new choice of hat has distinct military lines -- a small peak and high pleated crown. (Source: AP Photo, File)
Britain's Princess Elizabeth leaves Westminster Abbey in London, with her husband, the Duke of Edinburgh, after their wedding ceremony on Nov. 20, 1947. (Source: AP Photo, File)
Britain's Princess Elizabeth appears on the grounds of the Royal Lodge at Windsor, England, on Aug. 26, 1946. (Source: AP Photo, File)
Queen Elizabeth II crowns her son Charles, Prince of Wales during his investiture ceremony on July 1, 1969 at Caernafon Castle in Wales, as Britain's Home Secretary James Callaghan looks on. (Source: AP Photo, File)
Britain's Queen Elizabeth II and the Duke of Edinburgh leave the House Of Assembly after the Queen had addressed Bermuda's Colonial Parliament, in Hamilton, Bermuda on Nov. 25, 1953. (Source: AP Photo, File)
Britain's Queen Elizabeth II, then Princess Elizabeth, wears a silver gown with a diamond tiara and pearl necklace, in this Aug. 30, 1949 photo. (Source: AP Photo, File)
Britain's Queen Elizabeth II appears during the State Opening of Parliament in London in this April 1966 photo. (Source: AP Photo, File)
This combination of photos shows Britain's Queen Elizabeth II under an umbrella at a garden party at Buckingham Palace in London, on May 10, 2016, left, during her visit to the 'Wild London' exhibition in Richmond, west London on May 15, 2012, center, and leaving the British royal family's traditional Christmas Day church service at St. Mary Magdalene Church in Sandringham, England on Dec. 25, 2015. (Source: AP Photo)