Judi told Express.co.uk: “Charles grew up sandwiched between two remarkable women.
“Both his mother and his sister are hard-working, strong and stoic, with no outward signs of emotions like anxiety or self-doubt.
“Charles, on the other hand, has always shown signals that suggest self-pity and inner anguish.
“Growing up he and Anne perfectly defined the chalk-and-cheese sibling relationship, with Charles suffering through his school years while Anne just got on with things.
“As Charles adopted a more academic approach to the life of a future king, Anne became a successful, no-nonsense sportswoman alongside her regular royal duties.”
While they may have taken different approaches to their duties, being a royal seems important to both of them.
Princess Anne is often considered the hardest working royal and their commitment to the Queen could have brought the siblings closer together.
“Anne and Charles will probably never be the closest brother and sister,” the expert continued.
“However, they are beginning to look as though shared goals in terms of their love and sense of duty to their mother and a desire to sustain the image of the royal firm have brought them closer together.”
When the pair have been spotted together, Judi suggested their relationship is now more relaxed than it once was.
She continued: “Recently there does seem to be an element of affectionate humour between Charles and his sister and it will often include their mother.
“Charles still looks very earnest but Anne’s piercing eye-gaze and grin suggests some gentle mocking that in turn suggests he might not be taking himself too seriously these days.”
Princess Anne is also thought to have a good relationship with her sister-in-law, Camilla, Duchess of Cornwall.
Their friendship could have pulled the royal siblings closer together.
The expert continued: “Given their past histories, with Anne having dated Camilla’s ex-husband, the relationship between Anne and Camilla might have been difficult, creating a bigger rift between Charles and his sister.
“But in fact, the two women seem very tolerant of one another to the point of often looking like old friends, and this might have created an easing in the relationship between the siblings.”