As Prince William and Princess Kate approach their 14th wedding anniversary, their bond appears stronger than ever-having faced personal and public challenges, from King Charles and Kate‘s health battles to their well-documented tensions with Prince Harry and Meghan Markle.

However, according to royal author Tom Quinn, behind the scenes, Middleton plays a crucial role in keeping William grounded, particularly when he becomes “fractious” or frustrated.

In his latest book, Yes Ma’am: The Secret Life of Royal Servants, Quinn sheds light on William‘s alleged quick temper and how Kate manages to keep things under control.

“Protocol means suits must be pressed and laid out after a period of consultation the night before; shoes must be polished, ties chosen. Baths must be run at precisely the same time each day, and both King Charles and Prince William are prone to tantrums if things are not done to their liking,” Quinn writes.

One former royal staff member revealed that “they both get irritated very quickly. They are very picky. It comes naturally to them.”

However, the source emphasized that Kate is the one who calms William when things don’t go his way.

“I don’t know where William would be without Kate,” the source added. “She hasn’t had everything done for her throughout her life, so she calms him down when he gets a bit fractious. She said he sometimes has to be treated as her fourth child.”

While William and Kate‘s relationship is often portrayed as ideal, Quinn notes that they do have disagreements like any other couple.

“They do have rows. It’s not a perfect marriage. They have terrific rows,” Quinn told The Mirror.

“They don’t throw vases at each other. They throw cushions. It’s always kept under control.”