Princess Diana’s mom, Frances Shand Kydd, was notoriously “not cut out for maternity”, having left her children at a young age.

Frances was married to John Spencer, the 8th Earl Spencer. Together they had four kids, Lady Sarah McCorquodale, Jane Fellowes, Charles Spencer and Princess Diana. When Diana was 7-years-old, Frances and John divorced and Frances left her children.

Charles Spencer, 9th Earl Spencer, has now opened up about the difficult time they went through in an interview with The Sunday Times.

“Diana and I had two older sisters who were away at school, so she and I were very much in it together and I did talk to her about it,” he said, ahead of his book release The White Ship.

“Our father was a quiet and constant source of love, but our mother wasn’t cut out for maternity. Not her fault, she couldn’t do it,” Spencer, 56, continued. “While she was packing her stuff to leave, she promised Diana she’d come back to see her. Diana used to wait on the doorstep for her, but she never came.”

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It has taken Charles a long time to recover from the pain, telling the publication that he has been “in and out of therapy for 20 years.”

He added that the “agonizing and horrible” work on his “unhappy childhood” has “been cathartic.”

“Coming out the other side has been good,” he said. “The one thing I’ve learnt through all the stuff I’ve tackled is that very few people set out to be destructive.”

Charles, who is on his third marriage, said that going through the abandonment as a child as “left me with a predisposition for rescuing people.”

Fortunately, by the time he met his current wife, Karen, the therapy was working.

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“We got engaged quickly and I’m sure people thought, ‘Here he goes again,’ but I was confident,” he said of his wife who he married in 2011.

Karen, Countess Spencer, added, “The most appealing thing about Charles for me was how willing he was to work on himself, and continue to do so.”

“I love that we are a supportive partnership. We’re both ambitious, and there’s been a lot of give and take.”

The White Ship will be released on Sept. 17.