Prince Harry has put the acrimonious rift with his brother behind him to “reach out” privately after being told the Princess of Wales was undergoing treatment for cancer.

The Duke of Sussex made contact with both Prince William and the Princess on learning she had started a course of “preventive chemotherapy”, the Telegraph understands.

The Duchess of Sussex has also been in touch with the Prince and Princess amid reports the Sussexes were “blindsided” by the Princess’s announcement, which they learned of on Friday.

An insider told the New York Post: “They had no idea, and only learned of the news around the same time the rest of the world found out.

“This goes to show the irreparable damage they have caused. The trust has been broken and the royal family is OK distancing themselves from them.”

Sources close to the Sussexes declined to elaborate on when, or how, the couple found out about the diagnosis.

It is unlikely the Prince and Princess would have trusted the couple with the devastating news, which they kept within their very tight inner circle for several weeks to protect their three children.

Senior members of the Royal family lost all faith in the Duke and Duchess in the wake of their many television interviews and became “wary” of talking to the couple in case their words were repeated in public.

The Prince and Princess were said to have been devastated by the many intimate family revelations, text messages and conversations the Duke of Sussex shared in his memoir, Spare.

The Prince of Wales in particular, was angry about how his wife had been portrayed and was “mortified” his brother had betrayed them for commercial gain.

The two couples are not thought to have been in contact for many months.

The messages of support from California might therefore be considered an olive branch that could mark the beginning of a thawing in relations.

The Sussexes released a public statement conveying their good wishes to the Prince and Princess two and a half hours after their news became public knowledge.

“We wish health and healing for Kate and the family, and hope they are able to do so privately and in peace,” they said in a statement released shortly before 8.30pm on Friday.

When King Charles received his own cancer diagnosis, the Duke of Sussex was shaken enough to make a transatlantic dash to see his father.

The King had called the Duke personally to tell him the news, setting in motion their first proper face-to-face meeting after at least 17 months.

The Duke, who was at home in Montecito, wasted no time in booking a commercial flight to the UK and flew to London for a 30-minute meeting with the King at Clarence House on Feb 6.

However, the specific details of the meeting changed several times, as plans for the Duke to fly to Sandringham with the King and Queen were vetoed at the last minute.

Instead, he was forced to stay in a hotel – rather than a royal residence – and was not given police protection for the remainder of his short stay.

His next visit to the UK is scheduled for May, when the Duke hopes to attend a service at St Paul’s Cathedral to mark the tenth anniversary of the Invictus Games.