Prince Louis refused to heed his big sister Princess Charlotte's advice when they were watching the parade during Trooping the Colour, according to a lip reader.

Prince William and Kate Middleton's three children -- Prince George, 10, Princess Charlotte, 9, and Prince Louis, 6 -- joined Trooping the Colour on Saturday. It was also the first time the Princess of Wales was seen in public after she revealed her cancer diagnosis.

Princess Charlotte, Prince George and Prince Louis
(L-R) Prince George of Cambridge, Prince Louis of Cambridge and Princess Charlotte of Cambridge bow their heads as they receive a salute as the Royal Procession returns to Buckingham Palace during the Trooping the Colour parade the Trooping the Colour parade on June 2, 2022 in London, England. Jonathan Brady - WPA Pool/Getty Images

The Princess of Wales and her three kids appeared on the balcony to watch the parade. As the regiments, in their red ceremonial dress, continued to parade, Middleton could be seen whispering in her daughter's ear while the band played. Prince Louis was visibly delighted with the band and started dancing along with the Scots Guards to the "Highland Laddie" march. However, her big sister quickly reminded her to behave, but the younger royal refused.

"You have to stop doing that. Watch the parade," Princess Charlotte told Prince Louis, according to lip reader Nicola Hickling. "I won't," Prince Louis allegedly responded.

"Do as you're told," Princess Charlotte said. "Nope," Prince Louis added.

Prince William and Middleton's youngest child caught the public's attention once more due to his cheeky antics. He was seen tugging on the blind cords as Middleton watched his every move. And in his typical playful style, Prince Louis pulled on the white cord at the window instead of looking out at the crowd.

He was also later seen yawning while watching the parade from the window of the Duke of Wellington's former office. However, he was determined not to fall asleep and even danced through the show as Princess Charlotte politely watched the event.

Royal Family
Britain's King Charles III (R) looks at (L-2ndR) Britain's Prince George of Wales, Britain's Prince William, Prince of Wales, Britain's Prince Louis of Wales, Britain's Princess Charlotte of Wales, and Britain's Catherine, Princess of Wales, as they wave on the balcony of Buckingham Palace after attending the King's Birthday Parade "Trooping the Colour" in London on June 15, 2024. HENRY NICHOLLS/AFP via Getty Images

It wasn't the first time Princess Charlotte subtly told Prince Louis how to behave while they were in public, and he seemingly ignored her. At the 2022 Trooping the Colour, Prince George, Princess Charlotte and Prince Louis shared the carriage ride with Queen Camilla and their mom. During the ride, Prince Louis was ecstatic and waved nonstop to the public. Princess Charlotte subtly held his younger brother's wrist and put it down on his lap, so he would stop waving. However, after a few seconds, Prince Louis started waving again.

Princess Charlotte is Prince William and Middleton's second child and their only daughter. However, her dominance over her brothers has been observed over the years. Even the late Queen Elizabeth reportedly said she held the most authority among the siblings.

Royal Family
(L-R) Britain's Prince George of Wales, Britain's Prince William, Prince of Wales, Britain's Prince Louis of Wales, Britain's Catherine, Princess of Wales, Britain's Princess Charlotte of Wales, Britain's King Charles III and Britain's Queen Camilla stand on the balcony of Buckingham Palace after attending the King's Birthday Parade "Trooping the Colour" in London on June 15, 2024. HENRY NICHOLLS/AFP via Getty Images

Cameron Walker, GB News royal reporter, described Princess Charlotte as "feisty." She also reportedly knew how to behave appropriately because one time Prince Louis accidentally smacked her while they were on the balcony, and although she was visibly hurt, she didn't make a fuss about it.

"Charlotte knows the rules. She's the one in the middle. She knows how to keep everyone in good stead," Jo Frost, an author, global parenting expert and English TV personality known for the reality TV program "Supernanny," said of Princess Charlotte.

Princess Charlotte, Prince George and Prince Louis
 Britain's Princess Charlotte of Wales, Britain's Prince George of Wales and Britain's Prince Louis of Wales travel back to Buckingham Palace from Westminster following the coronation of King Charles III and Queen Camilla on May 06, 2023 in London, England. Justin Tallis - WPA Pool/Getty Images
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Prince Louis, Princess Charlotte, Trooping the Colour