Earl Charles Spencer and his wife Karen Spencer are calling it quits after nearly 13 years of marriage.

The younger brother of the late Princess Diana announced the split to The Mail on Sunday.

"It is immensely sad," the British aristocrat told the outlet about the divorce. "I just want to devote myself to all my children, and to my grandchildren, and I wish Karen every happiness in the future."

PRINCESS DIANA'S BROTHER, CHARLES SPENCER, REVEALS DEVASTATING FAMILY SECRET

Earl Charles Spencer in a suit next to Karen Spencer in a purple outfit and matching hat

Charles Spencer, 9th Earl Spencer, and Karen Spencer arrive at the wedding of Prince Harry and Meghan Markle on May 19, 2018, in Windsor, England. (Chris Jackson/Getty Images)

A spokesperson for Spencer didn’t immediately respond to Fox News Digital’s request for comment.

According to the outlet, the 9th Earl Spencer’s marriage to the Countess of Spencer ended amid the writing of his memoir, "A Very Private School." The pair first announced the breakup privately to their staff at Althorp House, Charles’ ancestral home, in April.

The outlet also reported that Spencer is "becoming close to" Norwegian archaeologist Dr. Cat Jarman. They "look very happy together" but it is still "early days."

Charles Spencer in a tux and Karen Spencer in a strapless red dress

Countess Spencer and Earl Spencer have been married for nearly 13 years. (Dave Benett/Getty Images for William & Son)

Jarman co-hosts the history podcast "The Rabbit Hole Detectives" with Spencer and Rev. Richard Coles.

Spencer and Karen, 52, said "I do" at Althorp House in June 2011. The wedding took place two months after Spencer’s nephew, Prince William, married Kate Middleton. Althorp House, the historic English estate where Spencer and his sister Diana grew up, became their residence upon marriage. They share a 12-year-old daughter, Charlotte Diana, whose name pays tribute to her royal aunt.

Karen, a social entrepreneur, is the founder and CEO of Whole Child International. She has two older daughters from her previous marriage to Hollywood producer Mark Gordon.

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Charles Spencer being embraced by Victoria Lockwood in a portrait

Charles Spencer was married to British model Victoria Lockwood from 1989 to 1997. (Tim Graham Photo Library via Getty Images)

Spencer, who has been married three times, shares four children with his first wife, Victoria Lockwood, and two children with his second wife, Caroline Freud.

In his memoir, "A Very Private School," Spencer revealed how he was sexually abused as a child. Over the years, Spencer kept the abuse a secret. But after two failed marriages, Spencer realized he needed help.

Charles Spencer in a light blue suit and tie walking in front of Caroline Freud in a red dress and black jacket

Charles Spencer was married to Caroline Freud from 2001 to 2007. (Dave Benett/Getty Images)

"I was so confused by my endless romantic disasters, deep unhappiness and two divorces," he previously told Fox News Digital. "I also wanted to do something for my children. Actually, that was the spur. I wanted to get better for them, so I could be a better father. I don’t know if they would agree that I managed it, but that was my aim. And I think, if I hadn’t been a parent, I probably would have just gone on... coping. [Saying it out loud] was surprisingly helpful. It didn’t get to the root of the problem, but it sent me on a course of more honest therapy."

Spencer said he’s "really turned a corner" in the last three to four months, especially after writing his book. He’s still doing "a very effective" post-traumatic stress disorder treatment, as well as Tai Chi and breathing exercises.

"I’ve got a whole armory of support techniques to try and get to a better place," he shared.

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A black and white childhood photo of Charles Spencer and Princess Diana

Lady Diana Spencer (1961-1997) (Diana, Princess of Wales) with her brother Charles, Viscount Althorp, (Earl Spencer) at their home, circa 1968. (Central Press/Getty Images)

Following the book’s publication, Spencer told People magazine that Karen "has been supportive."

"I think it was very challenging for her to have a husband going through what was essentially four and a half years of the most profound therapy with very difficult undertones to it," he told the outlet. "And she supported the idea of me doing it."

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"I think she always hoped I would come out happier and healthier," he continued. "And that seems to be the case very much. So, I'm grateful to have her standing by me while I went through this, what I now realize was an essential process."