How Prince William Is Coping With Kate Middleton's Cancer Diagnosis: Royal Expert

The Princess of Wales announced on Friday she's battling cancer and is undergoing preventative chemotherapy.

Prince William is doing his best to be a supportive husband, father and son amid Kate Middleton's recent cancer diagnosis revelation, which comes nearly two months after his father, King Charles III, also revealed his own cancer diagnosis. 

But a sense of optimism looms large at Kensington Palace, as royal expert Katie Nicholl tells ET that there are good signs indicating that Kate's bout with cancer is something the royal family will overcome. 

"We're told by the palace that Kate's feeling optimistic and that she's in good spirits," Nicholl says. "Hopefully the same can be said of Prince William, but clearly he's going to be desperately worried. This is his wife, his partner of some 20 years. The mother of his gorgeous three young children."

And as Kate leans on William for support amid these turbulent times, the same can be said about his father, Charles.

"There's huge pressure on the Prince of Wales. Not only is he having to step up for his father and support his father and the queen, but now having to care for his wife," Nicholl says. "Let's hope that she tolerates this chemotherapy well. There's every chance that she will. I think people hear the word 'chemotherapy' and they always think the worse. But there's every chance that she might sail through this treatment, as she's said that surgery has been successful. And knowing the couple, they always try to find the positive in everything. So, I think they will be feeling shocked, yes, but also positive."

In an on-camera statement, Kate shared that, following her abdominal surgery, it had been thought that the procedure would be non-cancerous but tests conducted after her surgery showed doctors "found cancer had been present."

She added, "My medical team therefore advised that I should undergo a course of preventative chemotherapy and I'm now in the early stages of that treatment."

Neither the palace nor Kate shared what type of cancer she's battling, only that she's now undergoing chemotherapy. Following the devastating news, a source told ET that Kate filmed the video on March 20, and she started receiving cancer treatment shortly after her surgery in January. In the video, Kate smiled at times while delivering the somber news.

"The princess looked pretty shell-shocked," Nicholl says. "I think she looked like a woman who has been through a huge amount in the last couple of months. We're so used to seeing her with her big hair and she's still got her beautiful, big hair, that lovely smile. She's still got that, but she did look like she has been through a tough time and I think that anyone that has undergone a cancer diagnosis knows just what an impact it has and, of course, not just the impact on her but the impact on her young family as well."

A source told ET that William and Kate struggled to tell their children -- Prince George, 10, Princess Charlotte, 8, and Prince Louis, 5 -- because they wanted to shield them as much as possible. 

"Children process information in different ways. Their primary concern was to be able to explain this to the children in a way that was reassuring, and they could process," the source said.

In her video statement, Kate said in revealing the cancer diagnosis she took her time because she needed to recover from major surgery "but, most importantly, it has taken us time to explain everything to George, Charlotte, and Louis in a way that's appropriate for them and to reassure them that I'm going to be OK."

With two senior members of the royal family now battling cancer, Nicholl says the pressure falls now on Queen Camilla, 76, as far as public appearances are concerned. 

"We've seen Queen Camilla carrying out a really busy schedule of engagement, standing in for the king at the Commonwealth Day Service in March, and there's also a huge amount of pressure on Prince William as well to step up to the plate," Nicholl explains. "The late Queen Elizabeth always said, 'I have to be seen to be believed,' and that mantra is as true now as it was then."

RELATED CONTENT: