Crown's Cold Case: Prince William's Frosty Message to Prince Harry Proves Sibling Hatred Is Hard to Hide

Prince William's reply to Prince Harry's message of support after Catherine, Princess of Wales revealed she was battling cancer, was reportedly "thick with frost."

"Harry and Meghan have been in contact with William, but their private message was simply one of sympathy and didn’t include any suggestion the brothers should make up and let bygones be bygones or that Harry should fly back to the U.K. soon," royal author Tom Quinn revealed.

"There is just too much ill feeling for that," he added. "William, who is still hurt by everything Harry has said in the past, has responded, but the response is very much engineered by the palace, and it’s hardly the kind of warm, informal response you would expect from one brother to another. It's more like the sort of communication you would get between two slightly wary diplomats."

This revelation follows reports highlighting how King Charles III is busy as Britain and several other nations' head of state, but the monarch is reportedly dedicated to mending the rift between his sons.

"That rift sounds like one that's going to be very difficult to mend," journalist Nigel Nelson told an outlet. "If it is mendable, who would be in a better position to mend it than their father?"

The King's death will immediately make William the new monarch, and reports now reflect a potential Montecito meltdown when the news one day hits.

"Because what would the repercussions be if Prince William pushed you out of the fold?" royal expert Kinsey Schofield told an outlet.

"I do think he would write about his family again," she added. "He was waiting to publish a book after [Queen Elizabeth died]. Originally they were saying there was going to be another publication after the [late] Queen died. I suspect that maybe he would release a book after his father passed away especially if Prince William continues to keep him at arm's length."

Other reports suggest the future king has decided it is time to "fully" sever all contact with his youngest brother.

"William is sensitive, he likes structure and has perseverance," Ingrid Seward, the author of William & Harry: A Portrait of Two Princes shared. "He does not give up easily. His relationship with brother Harry upset him more than he would care to admit. But he found it easier to cut ties rather than allow himself to be continually annoyed."

"His father got cancer and Kate had a serious abdominal operation," she added. "Later to announce she too had to have cancer treatment. William played both mother and father to the children while he carried on with his royal duties supporting the Queen in his father's absence. The traumas of the past year have made him a stronger person. He has become the kind of man Diana always hoped he would be. Kind considerate and able to take on whatever life throws at him."

Daily Mirror reported on Quinn's comments.