Catherine, Princess of Wales, better known as Kate Middleton, is relying on quite a few people during this perilous time, when both she and her father-in-law, King Charles III, are dealing with cancer diagnosis. When Kate announced her shocking cancer diagnosis, she shouted out her husband Prince William, their children, and her family. And while many of her friends were reportedly shocked by her diagnosis, one member of her inner circle has been by her side: her sister Pippa Middleton.