Prince William, Duke of Cambridge, Catherine, Duchess of Cambridge and Prince Louis of Cambridge stand on the balcony of Buckingham Palace during Trooping The Colour, the Queen's annual birthday parade, June 8, 2019 in London.

Britain's Prince William, Duke of Cambridge and Crown Prince of Jordan Al Hussein bin Abdullah pose for a photograph with children, including Syrian refugees, during a visit at the archaeological site of Jerash, Jordan, June 25, 2018.

Prince William, Duke of Cambridge visits the Dar Na'mah Centre - a project of the Princess Taghrid Institute (PTI) on June 25, 2018 in Amman, Jordan. The institute is a charity set up by Princess Taghrid to support women of all ages to develop their own livelihoods and thereby support their families and communities.

Prince William, Duke of Cambridge visits the Dar Na'mah Centre - a project of the Princess Taghrid Institute (PTI) on June 25, 2018 in Amman, Jordan. The institute is a charity set up by Princess Taghrid to support women of all ages to develop their own livelihoods and thereby support their families and communities.

Prince William, Duke of Cambridge and Crown Prince Hussein of Jordan visit the Jerash archaeological site on June 25, 2018 in Amman, Jordan.

Britain's Prince Harry, Duke of Sussex and Prince Harry's brother and best man Prince William, Duke of Cambridge wait in the chapel ahead of his wedding to US actress Meghan Markle at St George's Chapel, Windsor Castle, in Windsor, May 19, 2018.

Britain's Prince William and Kate, Duchess of Cambridge pose for a photo with their newborn baby son as they leave the Lindo wing at St Mary's Hospital in London, April 23, 2018.

Prince William, Duke of Cambridge and Prince Harry attend the wedding of Pippa Middleton and James Matthews at St Mark's Church on May 20, 2017 in Englefield Green, England.

Prince William attends the Royal Ascot, in London, June 20, 2017.

Prince William, Duke of Cambridge gives Queen Elizabeth II a tour as they open the new East Anglian Air Ambulance Base at Cambridge Airport on July 13, 2016 in Cambridge, England.

Prince William watches Nao the robot dance at the London 2016 Founders Forum in Watford, Hertfordshire, England, June 16, 2016. The conference and networking event is for the leading digital and technology entrepreneurs from the United Kingdom and around the world.

Britain's Kate Duchess of Cambridge signs a book of condolence for the Orlando nightclub shooting victims at the US Embassy in London, while Prince William looks on, June 14, 2016.

Britain's Prince Harry, Catherine, The Duchess of Cambridge and her husband, Prince William leave St. Paul's Cathedral in London June 10, 2016, after attending the National Service of Thanksgiving to mark the 90th birthday of Queen Elizabeth II.

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge arrive to greet guests attending a garden party at Buckingham Palace, May 24, 2016, in London.

Britain's Catherine, Duchess of Cambridge holds her daughter Princess Charlotte, Prince George, Britain's Prince William, Duke of Cambridge, Britain's Prince Harry and Britain's Queen Elizabeth II stand on the balcony of Buckingham Palace to watch a fly-past of aircrafts by the Royal Air Force, in London, June 11, 2016.

Prince William and Catherine, Duke and Duchess of Cambridge, and Prince Harry attend the launch of their Heads Together campaign to eliminate stigma on mental health at the Queen Elizabeth Olympic Park in London.

Prince William, Duke of Cambridge, and Catherine, Duchess of Cambridge, arrive in an open carriage to attend Day 2 of Royal Ascot on June 15, 2016 in Ascot, England.

A picture made available on March 7, 2016 shows Catherine, Duchess of Cambridge, Princess Charlotte, Prince George and Prince William, Duke of Cambridge posing for pictures as they enjoy a short private break skiing in the French Alps.

A picture made available March 7, 2016 shows Prince William, right,Duke of Cambridge cuddling his daughter Princess Charlotte of Cambridge as he and his family enjoy a short private break skiing in the French Alps, France, March 3, 2016.

This image released April 20, 2016 shows four generations of the Royal family, from left, Prince Charles, Queen Elizabeth II, Prince George and Prince William, the Duke of Cambridge, during a photo shoot for the Royal Mail in the summer of 2015 in the White Drawing Room at Buckingham Palace in London for a stamp sheet to mark the 90th birthday of Britain's Queen Elizabeth II.

Prince William, Duke of Cambridge, takes a penalty kick during a visit to The Football for Peace initiative at Saltley Academy on Dec. 7, 2015 in Birmingham, England.

Prince William, Duke Of Cambridge takes part in a group exercise during his visit to Hammersmith Academy to support the Diana Award's Anti-bullying Campaign, Sept. 21, 2015, in London.

Britain's Prince William, the Duke of Cambridge walks, with an East Anglian Air Ambulance (EAAA) in the background, as he begins his new role, at Cambridge Airport, Cambridge, in England, July 13, 2015.

Britain's Prince William, the Duke of Cambridge sits in the cockpit as he begins his new job with the East Anglian Air Ambulance (EAAA), at Cambridge Airport, Cambridge, in England, July 13, 2015.

Britain's Prince William, the Duke of Cambridge adjusts his helmet as he prepares to board an East Anglian Air Ambulance (EAAA), to begin his new job, at Cambridge Airport, Cambridge, in England,July 13, 2015.

Prince William, Duke of Cambridge receives an England football shirt for daughter Princess Charlotte of Cambridge from Captain Steph Houghton as he meets the England Women's Football Team at St George's Park, May 20, 2015, in Burton-upon-Trent, England.

Prince William, Duke of Cambridge receives an England football shirt for daughter Princess Charlotte of Cambridge as he meets the England Women's Football Team at St George's Park, May 20, 2015, in Burton-upon-Trent, England.

Prince William, Duke of Cambridge meets a rescued elephant called 'Ran Ran' at the Xishuangbanna Elephant Sanctuary, March 4, 2015, in Xishuangbanna, China.

Prince William, Duke Of Cambridge, rides a Brompton Bicycle during his visit to the GREAT British Festival of Creativity, March 3, 2015 in Shanghai, China.

Prince William, Duke of Cambridge wears a traditional Japanese King's Costume (Samurai) during a visit to the set of a historical drama at NHK Public Broadcasting Studios on Feb. 28, 2015 in Tokyo. The Duke of Cambridge is visiting Japan from February 26th to March 1st 2015.

Prince William, Duke of Cambridge meets NHK mascot 'Domo' during a visit to NHK Public Broadcasting Studios on the third day of his visit to Japan on Feb. 28, 2015 in Tokyo.

Britain's Prince William, right, waves with Tokyo Gov. Yoichi Masuzoe from a boat in Tokyo harbor after arriving in Tokyo, Feb. 26, 2015. William is on a four-day visit to Japan.

Sir Daniel Day-Lewis is made a Knight Bachelor of the British Empire by Prince William, the Duke of Cambridge, during an investiture ceremony at Buckingham Palace, London on Nov. 14, 2014.

Prince William, Duke of Cambridge plays a games console with young people as he visits the Access Centre during an official visit to Malta, Sept. 21, 2014, in Valletta, Malta.

Britain's Prince William and Camilla, Duchess of Cornwall, laugh during the opening ceremony of the Invictus Games at the Queen Elizabeth Park in east London, Sept. 10, 2014.

Prince William addresses cameras on Sept. 8, 2014, the same day that it was announced that his wife, Catherine, the Duchess of Cambridge, is pregnant with the couples' second child.

Prince William is seen at the controls of a Sea King helicopter as part of a search and rescue training exercise in Anglesey, Wales, March 31, 2011. The 32-year-old prince will join the East Anglian Air Ambulance as a pilot. Read More: <a href="http://abcn.ws/1sgYJVj" target="external">Prince William's New Job</a>

Britain's Prince William looks at a statute in honor of the first cartographer to circumnavigate Australia at Australia House, London, July 18, 2014.

Prince William, Duke of Cambridge lays a wreath during an official visit to the Coventry War Memorial Park, July 16, 2014, in Coventry, England.

Britain's Prince William, The Duke of Cambridge, snorkels with British Sub-Aqua Club (BSAC) members at a swimming pool in London, July 9, 2014.

Prince William, Duke of Cambridge plays in a charity polo match at Beaufort Polo Club, June 22, 2014, in Tetbury, England.

Catherine, Duchess of Cambridge, Prince William, Duke of Cambridge and Prince George of Cambridge leave Fairbairne Airbase as they head back to the UK after finishing their Royal Visit to Australia on April 25, 2014 in Canberra, Australia. William is celebrating his 32nd birthday Saturday, June 21, 2014.

Prince William, Duke of Cambridge and David Beckham pose together at the launch of United for Wildlife campaign at Google Town Hall on June 9, 2014 in London, England.

Madison Lambe's selfie taken with Prince William, Dec. 25, 2013 at Sandringham Estate in Norfolk, England.

Prince William, Duke of Cambridge, passes a volleyball with participants of a Coach Core apprentice training session at Westway Sports Centre, Dec. 4, 2013 in London, England.

Taylor Swift, Jon Bon Jovi and Prince William, Duke of Cambridge sing on stage at the Centrepoint Gala Dinner at Kensington Palace, Nov. 26, 2013 in London.

Prince William, Duke of Cambridge in his role as The President of The Football Association attends a coaching session at Buckingham Palace, Oct. 7, 2013 in London.

Prince William, Duke of Cambridge, attends day 1 of the Audi Polo Challenge at Coworth Park Polo Club on August 3, 2013 in Ascot, England.

Prince William poses proudly in his uniform after he qualified as a search and rescue operational captain, which means he can lead rescues for the Royal Air Force.

Prince William jokes around with his father, Prince Charles, on a 2004 trip to Madrisa Mountain in Klosters, Switzerland.

Prince William stands arm-in-arm with Catherine, Duchess of Cambridge for their engagement picture in November 2010. The couple married on April 29, 2011 in London's Westminster Abbey.

Prince William sits in a Royal Air Force Sea King helicopter after qualifying as a search and rescue operational captain.

Prince William smiles at a young baby while visiting with Royal Navy families at Churchill Square in Helensburgh, Scotland in 2007.

A young Prince William walks with his father, Prince Charles, in 2000.

Prince William clings to his father, Prince Charles, as they walk up the stairs of St. Mary's Hospital to see Princess Diana and Prince Harry in 1984.

Prince William clings nervously to an adult as he walks with a group of children.

Prince William joins his parents, Princess Diana and Prince Charles, on a park bench in 1984.

An adorable Prince William scratches his head curiously in this 1984 photo.

Prince Charles and Princess Diana smile at their eldest son, Prince William, Duke of Cambridge in this photo from 1983.

Princess Diana holds her son, Prince William, while her husband, Prince Charles, points to the camera during a royal tour in Alice Springs in March 1983.

In this 1983 photograph of William, the prince grins as he runs in the grass.

Diana, Princess of Wales, holds her oldest son, Prince William in June 1982.