At a celebration dinner for London’s Air Ambulance service, Prince William admitted that it’s been a difficult period for his family. “It’s fair to say the past few weeks have had a rather ‘medical’ focus,” he said, joking that he had come to an event for health care workers “to get away from it all.”

Like so many people around the world impacted by illness, William, 41, and his wife, Princess Kate Middleton, 42, who revealed that she was undergoing preventative chemotherapy for an unspecified cancer, are trying to stay positive. Keeping their three children, Prince George, 10, Princess Charlotte, 8, and Prince Louis, 5, feeling loved and secure during Kate’s convalescence and recovery is their highest priority.

When Kate’s doctor advised her of her condition following abdominal surgery in late January, she thought of the children first. “That’s why she didn’t want to share the news publicly,” explains a royals insider. “Her main concern was that they would hear about her illness from other children or overhear adults discussing it.” Instead, Kate and William made the united decision to release the news after their children began their Easter break from school.

Of course, they also faced the difficult task of explaining Kate’s condition to the kids in a way that wouldn’t scare or needlessly worry them. “Kate told it perfectly, saying that Mummy was sick but she’s getting better,” says the insider. “George and Charlotte took it more seriously and had more questions than Louis, but in the end, they believe their mother.”

After all the public speculation about her health and whereabouts, Kate also thought it would be best to go on camera and reveal her medical condition to the public herself, along with a plea for consideration of her young children. “We hope that you’ll understand that as a family we now need some time, space and privacy while I complete my treatment,” said Kate, who is not expected to return to her public duties right away.

Kate Middleton Is Leaning on Prince William Amid Cancer Treatment

The pressure has been intense on William, who is trying to stand strong for both Kate and his father, King Charles, 75, who is also being treated for an unspecified cancer. “William is stronger than most people give him credit for,” says the insider, who adds that the heir to the British throne has been tested before. He was just 15 when he lost his mother, Princess Diana, in a car accident. “William gets strength from Charles, and he also has a few core friends from Eton College and the University of St. Andrews that he talks to,” says the insider.

Kate Middleton told her kids about cancer
Samir Hussein/WireImage

Kate, who has prided herself on her ability to stand up to any situation, has been grateful to have William to lean on these past months. “She always knew her husband was supportive, but she has never seen this side of William,” says the insider. “He has stepped up in ways that have made her very proud.”

This season of challenges has also drawn the royal couple closer to Charles and Queen Camilla, who has stepped up her public appearances and been a strong booster for her husband. Even William’s estranged brother, Prince Harry, has sent a message of support to his family from California. “Harry has reached out and does plan on going back to England for a visit,” says the insider. “It is a time for family unity, of putting differences aside.”