On Saturday, Catherine, Princess of Wales, told her son's message to a group of kids who were playing outside Windsor Castle.
According to Louis's mother, Louis responded, "At least Grannie is with Great Grandpa now."As she relayed her son's comments, Princess Catherine praised them as "very sweet."
It wasn't the first time that Prince Louis had gone viral online; in June, he made headlines for his comical facial expressions when he pouted and acted out for his mother.
Princess Diana, Prince William, and Prince Harry and Meghan, Duchess of Sussex, were all present at Windsor Castle.
Large groups of people greeted the four as the two couples paid their respects to the queen.
Youngest son of Prince William and Catherine, Prince Louis may not have known the Queen for very long.