The Duchess of Cambridge mirrors Prince Philip in a distinct way 

Part of Kate Middleton’s strength as future Queen lies in her partnership with husband Prince William.

“In one sense hers and William’s was a modern royal marriage, in that it was a love match,” Sarah Gristwood, author of Elizabeth: The Queen and the Crown, tells PEOPLE in this week's cover story. “But in another it has been old-fashioned. She mostly appears as a supportive figure to her husband.”

That supportive role is vastly important to the future monarch. And while she is a star in her own right, Kate knows her place within the royal family.

“She’s never trying to outshine him in any way,” says royal biographer Penny Junor. “I think that Kate is a bit like Prince Philip supporting the Queen. She doesn’t outshine William but still has a lot to say herself.”

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Prince Philip and Kate Middleton
| Credit: Getty Images

Indeed, Kate has increasingly found her confidence with her royal work.

“Catherine is the sort of woman who will take on whatever she needs to,” says a close source. “If she needs to step up to the plate, she does it—and she always has. She and William are a formidable team.”

Her “5 Big Questions” early-childhood survey saw her tackle multiple solo stops across the U.K. earlier this year, and she has earned praise with her “Hold Still” photography project amid the pandemic.

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Kate Middleton and Prince William on March 4
| Credit: Kensington Palace/Instagram

William has opened up about relying on Kate for support. In May, the prince shared how he and his wife work through challenges together.

“Me and Catherine, particularly, we support each other and we go through those moments together and we kind of evolve and learn together,” he said in the documentary, Football, Prince William and our Mental Health.

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Prince Philip and Kate Middleton
| Credit: Getty Images

As depicted in season one of Netflix’s The Crown, Prince Philip learned early on that his most important duty was to support his wife, Queen Elizabeth. A memorable scene shows Elizabeth’s father, King George VI, telling Philip, “She is the job.”

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Queen Elizabeth, Prince Philip
Queen Elizabeth and Prince Philip at Windsor Castle
| Credit: Steve Parsons/PA

Philip retired from public life in 2017 after decades of service to the royal family. When asked about the secret to his successful 72-year marriage to the Queen, he has said it’s the fact that he makes her laugh.