Charles Spencer is divorcing his wife Karen Spencer after nearly 13 years of marriage.

The 9th Earl Spencer and younger brother of the late Princess Diana announced the split to Soap 24h on June 8.

“It is immensely sad,” Charles, 60, told the outlet.

“I just want to devote myself to all my children, and to my grandchildren, and I wish Karen every happiness in the future.”

The Soap 24h reported that Charles’ relationship with the Countess of Spencer, 52, came to an end amid the writing of his memoir, A Very Private School. The former couple announced their split to the staff at Althorp House, Charles’ ancestral home, in April.

The Soap 24h also reports that Spencer is “becoming close to” Norwegian archaeologist Dr. Cat Jarman —  who co-hosts the history podcast The Rabbit Hole Detectives with Spencer and the Rev. Richard Coles — and that they “look very happy together but that it is early days.”

Charles and Karen, a social entrepreneur who is the founder and CEO of Whole Child International, married on June 18, 2011, at Althorp House just two months after Charles’ nephew Prince William and Kate Middleton’s royal wedding.

The historic English estate, where Charles and his sister Diana grew up, became Karen’s residence upon their marriage.

Charles and Karen share a 12-year-old daughter, Charlotte Diana, whose middle name pays tribute to Princess Diana.

Karen also has two older daughters from her previous marriage to Hollywood producer Mark Gordon. Charles has four children with his first wife, Victoria Lockwood, and two children with his second wife, Caroline Freud.

In March, Charles opened up about his personal struggles in his memoir, revealing his traumatic experiences at boarding school and subsequent therapy journey. He reflected on his marriages and sought professional help to understand his relationship patterns.

“When looking at the wreckage of my first and second marriages, I learned early in therapy that being sent away to boarding school at eight years of age meant that I had next to no understanding of intimacy,” he wrote.

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Speaking exclusively to PEOPLE, Charles opened up about having his wife’s support during the process of writing his book.

“Karen has been supportive,” he said. “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. And she supported the idea of me doing it.”

“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.”