Incredible -King Charles warned Prince William, ‘Don’t make the mistakes that I made’ in marriage:..See More 👇

Prince William received a warning about his marriage from his father, King Charles.

“[His father] said, ‘Look, William, there’s nothing more important than your family,’” Ingrid Seward, editor-in-chief of Majesty magazine and author of “My Mother and I,” told Fox News Digital.

“’Don’t make the mistakes that I made,’” Seward claimed he said. “I just did duty, duty, duty. I neglected my marriage, and look what happened.’”

And there are lessons to be learned from the king’s past.

Charles met Camilla Parker Bowles at a polo match in 1970. The two became close, but their romance was interrupted by his eight months of naval duty. In his absence, Camilla married her longtime boyfriend, army officer Andrew Parker Bowles, in 1973.

In 1981, Charles married Lady Diana Spencer. The union was plagued with problems and scrutinized by the tabloids.

Camilla and Andrew divorced in 1995, shortly after Charles gave an explosive interview admitting an affair with his former love. Charles and Diana’s divorce was finalized in 1996, a year before the princess was killed in a car crash at age 36.

His father] said, ‘Look, William, there’s nothing more important than your family. Don’t make the mistakes that I made. I just did duty, duty, duty. I neglected my marriage and look what happened.’”

William met Kate Middleton when they were students at St. Andrews University in 2001. The following year, they moved in together with friends. The couple eventually moved into a place of their own in 2003, a year before their relationship went public.

The couple parted ways in 2007 after nearly five years of dating and got back together later that year. William proposed to Kate in 2010, and the couple married in 2011.

The Prince and Princess of Wales share three children — Prince George, Princess Charlotte and Prince Louis. William is heir to the British throne.

Seward said Charles is a “big supporter” of the union and encouraged William to put duty aside when Kate was faced with a major health blow.

In January of this year, Kensington Palace announced Kate underwent a “planned abdominal surgery.” William postponed official royal duties to be by Kate’s side and support their family.

After the princess became the subject of online conspiracy theories surrounding her health, the 42-year-old announced in March that, following her operation, “cancer had been present.”

After Kate’s announcement, William took time off to support his wife.

In September, Kate announced she was cancer-free. The princess, who appeared alongside her husband and their children, described how difficult the past nine months had been for her family. She expressed “relief” at completing her course of treatment.

I think she’s had fantastic support from Prince William,” said Seward. “He publicly said it’s been the toughest year that he’s ever had, and it’s been very … difficult. So, we can only imagine how difficult it [really] must have been because William also [had] to reassure their three young children that mummy’s going to be OK. Kids get very worried when they see their parents unwell, especially for such a length of time.”

“I think it’s been very tough, and he has been an enormous support,” Seward shared. “And, in turn, he has been supported by his father.”

In her video announcement, Kate said she was “looking forward to being back at work” but was planning to “take each day as it comes.” Seward noted Kate had been “holding up really well.”

Kate Middleton in a burgundy coatdress standing next to Prince William in a suit and matching tie and smiling.

“She’s not really doing evening engagements,” said Seward. “The only evening engagement she has this week is her very own carol service at Westminster Abbey, which is being recorded to be televised on Christmas Eve.”

People Magazine reported that Kate reached out to each of the 1,600 guests who will gather in Westminster Abbey Dec. 6 with an emotional letter.

In it, she described how the holiday season is one of her favorite times of the year.

“It also gives us the opportunity to slow down and reflect on the deeper things that connect us all,” she shared, as quoted by the outlet. “It is when we stop and take ourselves away from the pressures of daily life that we find the space to live our lives with an open heart, with love, kindness and forgiveness — so much of what the Christmas spirit is all about.”

She also shared that the story of Christmas “reminds us of the importance of giving and receiving empathy, as well as just how much we need each other in spite of our differences.”

“Above all else, it encourages us to turn to love, not fear,” said Kate. “The love that we show ourselves and the love we show others. Love that listens with empathy, love that is kind and understanding, love that is forgiving and love that brings joy and hope.

“It is this love which is the greatest gift we can receive. … Love is the light that can shine bright, even in our darkest times. We all have something we can offer one another. Gentle words or a receptive ear, an arm around an exhausted shoulder, or silently being by someone’s side.”

Kate’s carol service “is a heartfelt celebration of every one of you, and a reminder that at Christmas, and throughout the year, we must all shine for each other,” she said.

“Because in times of joy and sadness, we are all each other’s light.”

WATCH: KING CHARLES GAVE THIS WARNING TO PRINCE WILLIAM ABOUT MARRIAGE: AUTHOR

The outlet noted that Kate and William, 42, will be joined by other members of the royal family. It’s also likely the couple will bring their three children as they have in the past.

“I think that Catherine has a huge warmth for other people, which is something that [her mother-in-law Princess] Diana had too,” said Seward. “I think she’s completely genuine, and I think she feels that if she’s doing something for others that really is going to help them, that makes everybody feel good.

“I think that she will very much concentrate on that in the future,” Seward shared. “She’ll just do what she can. I think that when you are ill, as she has been — remember, she didn’t just have cancer, she also had an abdominal operation — I think it must’ve been very frightening.

I’m sure she’s doing exactly what her medical team is saying … and they always say the same thing. They say, ‘Rest, rest, rest.’ I think she’s following that, and she’ll do what she can when she can.”