But how is the relationship between Camilla and Sophie in the current Royal Family?
Body language expert Judi James spoke exclusively to Express.co.uk about the relationship between the two wives of that royal generation.
Judi asked, “Could they be suffering from ‘First Wives Club’ Syndrome?
“Despite being sisters-in-law, there are few, if any, moments of body language between Sophie and Camilla that suggest anything warmer than a courteous and even quite formal relationship.
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“There is no reflection between them that hints at a natural empathy or like-mindedness.
“In addition, there is nothing that defines similar or complementary personalities,” said the expert.
Judi extended Sophie’s warm relationship with other members of the Royal Family.
She suggested: “Sophie tends to be very open about her signs of friendship.
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“She is a fun and active warmth at all levels of the royal firm, from the Queen herself on down.
“His relationship with Kate especially resembles a spontaneous friendship and they are often seen chatting and engaging as if they really enjoy each other’s company.
“But with Camilla, there seems to be an air of polite detachment.
“It is as if the two women happily talk and acknowledge each other in public, but without escalating their rituals and displays to hint at stronger bonds,” Judi added.
Sophie and Camilla rarely attend royal engagements together unless the event involves multiple royals.
For example, in recent years they have only been photographed together attending Trooping the Color or the annual Festival of Remembrance.
These are the only times the two are photographed together, suggesting a “formal relationship,” as Judi put it.
Camilla is 74 years old, while Sophie is 56, so the two royal ladies belong to completely different generations.
Sophie is raising Lady Louise Windsor and James, Viscount Severn, aged 18 and 14.
Meanwhile, Camilla already has 10 grandchildren of her own.
He has five grandchildren from his two children, Laura Lopes and Tom Parker Bowles.
However, Camilla is also the adoptive grandmother of Prince William and Prince Harry’s children, Prince George, Princess Charlotte, Prince Louis, Archie Mountbatten-Windsor, and Lilibet Mountbatten Windsor.