It has created problems not only when Prince Charles and Princess Diana ended their marriage in the most bitter fashion in 1996 but also when other royals - Princess Margaret - fell in love with people who had been divorced and could not marry them for that reason.
The British monarch also serves as Supreme Governor of the Church of England, which historically refused to bless the unions of anyone with a living ex-spouse. The church softened its position in 2002 to allow divorced individuals to remarry under "exceptional circumstances."
In 1936, drama over a divorced American woman led King Edward VIII to abdicate the throne because of his determination to marry her.
In contrast, in 2018, Prince Harry's plan to marry divorced American actress Meghan Markle is being met with ... a shrug.
Here's a look at royals and divorces:
HENRY VIII AND HIS SIX WIVES
Henry VIII's desire to divorce his first wife was central to his reign. He tried but failed to gain the pope's approval to annul his marriage to his first wife, Catherine of Aragon, then broke with the Catholic Church. In 1533 the marriage was declared invalid, freeing Henry to marry again.
He eventually married six times and divorced twice. Two of his wives were beheaded; one died shortly after childbirth; one died in detention, and the two others outlived Henry, who died in 1547.
THE LAST TIME A SENIOR ROYAL MARRIED A DIVORCED AMERICAN
King Edward VIII provoked one of the greatest crises to face the modern British monarchy when he proposed to Wallis Simpson shortly after he ascended to the throne in 1936.
She was an American who had been divorced once and was in the process of divorcing her second husband. Given the tenor of the time, the marriage was deemed politically and socially unacceptable for the man who would head the Church of England.
Edward finally decided he had to choose between marrying the woman he wanted to spend his life with and his position as king. He chose love - and stepped down after one of the briefest reigns in British history.
TRUE LOVE DENIED DUE TO DIVORCE: PRINCESS MARGARET
Group Captain Peter Townsend was a World War II flying ace, an aide to King George VI - and devilishly handsome. He was also, unfortunately, divorced when he fell in love with Princess Margaret, the younger sister of Queen Elizabeth II.
The romance - Townsend proposed marriage, and Margaret was inclined to accept - put the young queen in a difficult position, given the social atmosphere of the time and her role as head of the Church of England, which did not allow divorced people to re-marry in the Church if the former spouse was still alive.
The British government sought to discourage the marriage, and Margaret eventually buckled in 1955, saying she had decided not to marry Townsend.
She eventually married Antony Armstrong-Jones, who became Lord Snowdon. The couple had two children - but divorced in 1978 after 18 years together.
The queen had been reluctant to approve her sister's marriage to a divorced man but - in a more tolerant era - has given her royal consent to the marriage of Harry and Markle.
Royal historian Hugo Vickers says Markle might have been found unsuitable in Margaret's time on several counts: She is divorced, with an ex-husband still alive; at age 36 she is older than the 33-year-old Harry, and she comes from a biracial background.
"It would have been probably terribly difficult for her to have married into the royal family in the 1950s, when I think any of the things that I mentioned might have been in a way played against her, but times move on," said Vickers.
PRINCE CHARLES AND CAMILLA: THE TIMES THEY ARE A-CHANGING
By the time Prince Charles married Camilla Parker-Bowles in 2005, Britain's social climate had changed to the point that the divorced heir to the throne could marry a divorced woman who had long been his lover. But the couple did not marry in a church, choosing instead a civil ceremony at the Windsor Guildhall, which is outside the grounds of Windsor Castle.
In another compromise, Charles' mother, the queen, did not attend the ceremony, at least in part because of her role as the head of the Church of England, which frowns on divorce. But she and her husband Prince Philip did attend a formal church blessing of the marriage after the ceremony.
Charles and Camilla also tried to soothe public sympathies for his first wife, the late Princess Diana, by saying Camilla would not take the title of queen when Charles becomes king. Instead she is known as the Duchess of Cornwall.
In all, three of the queen's four children - Charles, Princess Anne and Prince Andrew - have been divorced.
NEW ERA FOR HARRY
All of these concerns have faded away as Harry prepares to marry the divorced Markle on Saturday.
Not only will the couple wed in St. George's Chapel on the grounds of Windsor Castle, but the ceremony will be performed by the archbishop of Canterbury, Justin Welby, who leads the Church of England and the Anglican Communion worldwide.
"Times have moved on a lot and the royal family has moved on with them," said Kim Darroch, Britain's ambassador to the United States. "The Church has moved on as well and there are a lot of features of modern life that would have been difficult to imagine 50 years ago."
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