King Charles Privately Congratulates President Jimmy Carter on Turning 100

King Charles is among the many celebrating former President Jimmy Carter's milestone 100th birthday.

PEOPLE understands that the King "expressed warm personal greetings and great admiration" for Carter's lifetime of duty and public service, according to a spokesperson for the monarch. In a private message, the King congratulated Carter on becoming the first former president to become a centenarian.

Carter, who turned 100 on Oct. 1, served as U.S. president from 1977 to 1981 and during that time met the King's parents Queen Elizabeth and Prince Philip in 1977. Both Queen Elizabeth and Prince Philip also almost lived to see 100.

Prince Philip died in April 2021, less than two months shy of his 100th birthday. The Queen died in September 2022 at 96 years old.

The former president, the late Queen and late Duke of Edinburgh had dinner together in Buckingham Palace following a NATO Ministerial Meeting at Lancaster House in London, according to the White House Historical Association.

Associated Press reports that at the dinner, when the Queen Mother arrived, Carter "broke away, took her by the hand and escorted her to the assembled line of guests." The Queen Mother would herself live to 101 and died in March 2002.

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Carter, who became the longest-living president in March 2019, began receiving hospice care in February 2023. Not long after, it was revealed that his wife of over 75 years, Rosalynn Carter, had been diagnosed with dementia.

The former first lady died in November 2023, and Carter made a rare public appearance at her funeral service later that month.

He wore a blanket that had his wife's face stitched onto it, paying homage to their decades-spanning love story — which was not much different than the King's parents, who were married for over 70 years themselves.