King Charles and Catherine, Princess of Wales' close bond has been "comforting and reassuring" for them as they both go through cancer treatment.
The 75-year-old monarch and his daughter-in-law have "always been close" but their recent health issues have seen them grow even closer to one another, particularly when both were being treated at the London Clinic in January.
According to the Daily Telegraph newspaper, both were staying on the same floor, in a sealed-off area protected by security, with Charles - who was being treated for an enlarged prostate when his cancer was detected - able to make the short stroll along the corridor to visit Catherine following her major abdominal surgery.
A source told the outlet: "I think it was nice for them."
Another insider added: "What we've seen in recent weeks is that because they are both going through the same health experience, it's cemented that bond."
The relationship between Charles and his wife, Queen Camilla, and Catherine and her husband, Prince William, is said to be "genuinely warm" and supportive, and the monarch was keen to allow his son time to look after his wife and three children without pressuring him to "step up" take on more duties while he is away from public engagements due to his own health struggles.
A source said: "They have a very strong, genuinely warm relationship."
And an insider said of William: "You can imagine what he must personally be going through.
"His wife is the centre of his world. His father is ill. He has got a lot on his plate."
Catherine revealed in a video message on Friday (22.03.24) she was undergoing preventative chemotherapy after cancer was detected following her surgery and both she and the king, as well as their spouses, wanted to speak openly after supporting cancer charities, patients and affected families over the years.
A friend said: "They have chosen to be honest [about diagnosis] in the hope it would support other families. After all, what is more relatable than facing an illness that so many others will have experience of?"