Siblings with their partners must stand in order.
It was surprising for the media and the fans to see Meghan Markle standing behind Kate Middleton on the official trooping the color debut. But guess what the royal family’s rule is; that the siblings have to stand an order with their partners, which now makes it clear why the brand new Duchess of Sussex was standing behind her sister-in-law.
Prince William, the older in the family and the most senior brother, was the first in the appearance, followed by Kate Middleton then the others. It’s the Royal rules and etiquette that are to be followed by the royal family, and hence who are we, the commoners, to question.