On Sunday, Kate Middleton will turn a significant age.

The Duchess of Cambridge made strides on the international stage last year, taking on solo initiatives including the Westminster Abbey Christmas Carol service and Hold Still.

Despite her accomplishments, the 39-year-old mother of three is a "natural introvert," which makes it tough for her to socialize with powerful individuals like US President Joe Biden and First Lady Jill Biden.

During the COP26 meeting and Earthshot awards, Kate met with Canadian Prime Minister Justin Trudeau, German Chancellor Angela Merkel, and other world leaders.

Kate's role as a member of the royal family requires her to interact with high-profile personalities on the international stage. She went to a school with Dr. Jill in June 2021.

A close friend of Prince William's wife said the Hello magazine, "She still finds it quite challenging to mix with those sorts of players [the Bidens] because she's a natural introvert."

However, even with a trait like that, Kate is still on track to what her future will be.

"But she's really growing into the role," the friend said of Kate Middleton as future Queen in the making.

Her presence continues to be "understated," adding that she is "quietly growing in confidence" even after ten years of marrying into the British royal family.

Kate isn't the type of person who puts herself out there, according to the nameless buddy, so public speaking isn't her strong suit or something she loves.

But the Duchess of Cambridge reportedly knows that "it's an important way for her to make a positive contribution and there are times that you need to get out there and speak for things you believe in."

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40th Birthday Party Plans of Kate Middleton

Kate Middleton will be 40 on Sunday, but instead of throwing a lavish party, the Duchess of Cambridge is said to be planning a quiet gathering with close friends and family.

Royal author Duncan Larcombe told the Daily Mail,"There are likely to be low-key celebrations for the Duchess."

"She didn't want anything flashy anyway, that's not exactly her thing, but particularly given the current climate anything is likely to be scaled down."

It is also expected that her husband, Prince William, and their three children, Prince George, Princess Charlotte, and Prince Louis, will be spending the day with her.

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