According to Prince Harry writing in his shock memoir Spare, then-Prince Charles told Princess Diana after she gave birth to their youngest son, "Wonderful! Now you've given me an heir and a spare—my work is done."
Though we will never know whether this exchange truly happened or not, it illustrates one certainty among the British Royal Family: Over the course of history, there was often a "spare" who was pitted against the heir to the throne, and who became rebellious as a way to create their own identity.
This was the case with Princess Margaret, then with Prince Andrew, and now famously with Prince Harry. But for one royal expert, Prince William and Princess Kate are doing their utmost to not let this happen among their own children, Prince George, Princess Charlotte and Prince Louis.
"William and Catherine are determined to break the heir and the spare cycle," Kinsey Schofield told the Daily Star.
"I don't believe the word 'spare' has ever been uttered inside their home to describe one or more of their babies. It is just not on their radar. They wanted to have a large loving family."
Instead, the Prince and Princess of Wales are preparing their children for royal life as best they can.
"William and Catherine are teaching their children about royal responsibilities through doing them," Schofield continued.
"You will notice how poised and prepared the children seem to be during large royal engagements. You can tell that Princess Charlotte takes great pride in her family and responsibilities. [It reminds] me of the Princess Royal."
This preparedness was definitely visible on the kids' last public appearance during their grandfather's Coronation on May 6.
