Queen Elizabeth II named his grandson Prince William and Kate Middleton as the Duke and Duchess of Cambridge after they became officially married in 2011.
With that, all eyes were on the future king and queen as they took on more responsibilities in the British monarchy.
The Royal Rebel
However, little did the public know that the second in line to the throne broke a royal protocol during his wedding.
Prince William asked his younger brother Prince Harry to be his "best man" for his big day.
Prince Harry served as best man to The Duke of Cambridge at his wedding to Miss Catherine Middleton in 2011. pic.twitter.com/klHGqeAyeb — Kensington Palace (@KensingtonRoyal) April 26, 2018
Traditionally, instead of best men, the royal family calls those who are with the groom as "supporters."
Royal commentator Richard Fitzwilliams explained that logically, the royals will choose any of their siblings or closest relatives.
"Royals can pick who they like to be the best man, but it would only be natural to choose a sibling or relative. It depends on the circumstances," Fitzwilliams told The Standard.
In 2011, The Telegraph also cited that when Kate walked down the aisle at Westminster Abbey, Prince Harry mentioned a touching statement to his older brother.
"You are alright; she is here now," the younger royal whispered to his brother.
Prince William, on the other hand, had to wait for four minutes before he could turn around to check his bride, who was at the end of the aisle.
Prince Harry -- who was 33-years-old at that time -- also did the same thing and returned the favor.
When he and Meghan Markle married in May 2018, Prince Harry chose the Duke of Cambridge to be his best man for his wedding. It was also confirmed by Kensington Palace.
"Prince Harry has asked his brother The Duke of Cambridge to be his best man at his wedding to Ms. Meghan Markle. Prince Harry served as the best man to The Duke of Cambridge at his wedding to Miss Catherine Middleton in 2011. The Duke of Cambridge is honored to have been asked, and is very much looking forward to supporting his brother at St George's Chapel, Windsor on May 19th," the Palace statement read.
Moreover, in previous reports, as Prince William "wished'' Meghan and his brother on their big day, the Duke of Cambridge made a hilarious revelation about Prince Harry.
"We're very excited, delighted for them both. We're wishing them all the happiness in this very exciting time," he said before adding: "Personally, I hope it means he stays out of my fridge and will stop scrounging my food, which he's done for the last few years."
Contrary to the two royals, their father Prince Charles went for the more conventional type royal wedding and asked his brothers Princes Edward and Andrew to be his supporters when he married the late Lady Diana Spencer in July 1981.
Same goes with Queen Elizabeth II's youngest son, Prince Edward, when he married Sophie Rhys-Jones in June 1999 in St George's Chapel at Windsor Castle.
His "supporters" were his brothers, the Prince of Wales and the Duke of York.