In her video message revealing her cancer diagnosis, Princess Kate Middleton admitted it’s been a very challenging period. “It has been an incredibly tough couple of months for our entire family,” she confessed.

It’s a tragic coincidence that Kate is being treated for cancer at the same time as her father-in- law, King Charles ​III, but these difficulties have brought the pair closer. “They feel less alone together,” a royal insider tells Closer exclusively. “Kate would have been there for Charles no matter what, of course, but now when she finds something that gives her comfort — like a new TV show that takes her mind off of everything — she makes certain to share it with Charles.”

When Kate, 42, first met Queen Elizabeth II, she felt understandably nervous, but even now that Charles has ascended the throne there is a comfort between them born of longtime familiarity. “Kate has been in Charles’ life for 20 years!” notes the insider, adding that she first met him when she started dating Prince William in college. If she’s feeling unwell, she doesn’t have to pretend in front of Charles. “The comfort is there. They can sit on the couch together and talk about what’s going on in their lives.”

At this difficult time, Kate has often felt more worried for Charles, 75, than for herself. In February, Buckingham Palace announced that the king’s doctors detected cancer following his treatment for an enlarged prostate. Like Kate, the king has largely stepped away from his public duties while he undergoes treatment. “Kate knows she’ll be OK, so she is very focused on Charles and his journey back to health,” says the insider, who added that she also worries about William. “She doesn’t want her husband to lose another parent.”

Like Charles, Kate was being treated for another ailment when her cancer was detected. She went into the hospital in January for an unspecified abdominal surgery and tests discovered an “early stage” cancer. Kate began a course of chemotherapy as a preventive measure.

Inside Kate Middleton and King Charles' Bond as They Battle Cancer
Samir Hussein/WireImage

Before going public, she sat down with Charles for a private lunch that became very emotional. “The king has always had a close, warm and unique relationship with the princess,” says another source. “He has been encouraging and supportive of her throughout.”

Family Ties

Charles also looks forward to visits with Kate. “She has a knack for lifting his spirits,” says the first insider, explaining that she often sends Charles articles on topics she knows he’ll find interesting, like organic gardening, to make him smile. “If she reads about a beautiful place they can visit together, she shares that with him, too.”

Charles is always eager to hear about his grandchildren, Prince George, Princess Charlotte and Prince Louis, so Kate is delighted to fill him in. “Kate had the kids make Charles get-well cards and little crafts,” says the insider. “It’s so nice and so well received by Charles.”

With the end of the school year fast approaching, Kate is optimistic that everyone will be well enough to visit the Balmoral estate together this summer. “Kate hopes to spend time there with the kids, William and Charles before the rest of the extended family arrives,” explains the insider. “In so many ways, Kate is the daughter that Charles never had. She keeps his spirit up by looking forward to the future.”