Queen Elizabeth is among the world leaders to reach out to Joe Biden as he prepared to take the office of President of the United States.

The 94-year-old monarch sent a private message to Biden before Wednesday's inauguration, a Buckingham Palace spokesperson confirmed to Bazaar.

The rep maintained that the contents of the letter will stay between Biden and the royal.

A relationship in some form has existed between the Queen and America's presidents over the past few decades, as she's met with each of them since the beginning of her reign, save for Lyndon B. Johnson, the outlet reports.

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The Bidens already has ties to the royal family as Dr. Jill Biden and Elizabeth's grandson Prince Harry have interacted on a number of occasions.

Queen Elizabeth II of England has sent a private letter to President Joe Biden (left). (Getty Images)

According to Bazaar, Harry, 36, attended a reception for British and American wounded servicemen and women in 2013, via an invitation from Dr. Biden.

The following year, the educator was invited to Harry's Invictus Games and was spotted speaking to the prince on multiple occasions.

President Biden himself also spent time with Harry during the 2017 Invictus Games and in 2014, recalled to Guardian that he had read that "everywhere Prince Harry went, he had this blonde woman on his arm" in reference to the friendship between Dr. Biden and Harry during previous meetings.

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"The vice-president's wife! I'm a little worried here, you know what I mean?" he joked in the interview.

The Grand Duke of Luxembourg also reached out to Biden on the day of the inauguration and published the letter online.

Henri, Grand Duke of Luxembourg also sent a letter to Joe Biden on the day of his inauguration. (Photo by Luc Castel/Getty Images)

In his correspondence, Grand Duke Henri sent his "sincere congratulations" on behalf of himself, his wife, Maria Teresa, and "the Luxembourgish people."

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"Given our countries’ shared commitment to democratic ideals, it was disheartening to witness the recent attacks on the American institutions, which culminated in the storming of the Capitol," he said. "I have strong faith that under your Presidency democracy will prevail."

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Henri added that he is looking forward to "continuing and strengthening the longstanding relationship and deep friendship between our two countries."