King Charles' birthday turned into 'absolute nightmare' by Prince William and Prince Harry

It is a big day for King Charles today as he marks his 76th birthday - and several years ago on his landmark 70th birthday, a heartwarming photo of him surrounded by his family was released, but behind the scenes tension was brewing

His day today might be filled with the usual royal duties of public appearances and dealing with state papers - but no doubt King Charles will also carve out time to celebrate his birthday.

The monarch, who is undergoing treatment for cancer, turns 76 today and will mark the ocassion by opening several food distribution hubs as it also marks the first anniversary of the Coronation Food Project. His birthdays are usually low-key affairs but five years ago when he turned 70, Charles decided to celebrate the day by releasing several gorgeous family photos.

In them, he proudly sits beside wife Queen Camilla with his sons Prince William and Prince Harry also in the photo along with the Princess of Wales and the Duchess of Sussex. His three oldest grandchildren - Prince George, Princess Charlotte and Prince Louis - are also in the snap, although Prince Archie and Princess Lilibet missed out as the photo was taken before they were born.

But while fans loved the rare family shots, it was reportedly an "absolute nightmare" to arrange as William and Harry made very little effort in making sure the shoot happened, a book claims. In the bombshell biography Finding Freedom, authors Omid Scobie and Carolyn Durand claimed that the royal brothers "can be hot and cold with their father".

The authors wrote: "The boys can be hot and cold with their father' disclosed a source, who gave the example of planning the photo session for Charles' 70th birthday, which they called 'an absolute nightmare'. Neither William nor Harry made much of an effort to make themselves available, the source said."

Two photos from the photoshoot were released, the first a more formal snap and the second a candid picture which shows the family laughing. However, since that day, it seems the two brothers have gone on to have very different relationships with their father.

Despite their sometimes bumpy relationship, Charles and William are now said to have a bond "built on love, affection and respect". The pair both share a passion for tackling climate change and William publicly pledged his allegiance to his father at the Coronation last year.

However, Harry's relationship with his father seems to have deteriorated and he has been quite outspoken about the fractured bond with Charles. During a bombshell interview with Oprah Winfrey, Harry accused his dad of refusing to take his calls and claims he cut him off financially.

Earlier this year, a source claimed the pair are no longer speaking with one long-running issue seeing their estrangement deepen. Sources close to the Sussexes have now claimed that Harry's calls to his dad are going unanswered as Harry tries to discuss his security arrangements with his father. The Duke has been embroiled in a long-running battle over his security when he comes to the UK after he automatically lost the right to his police protection when he stepped down as a working royal.

He has lost his subsequent court battles to have it reinstated for him, wife Meghan and their two children and is planning an appeal. According toPEOPLE magazine, Harry believes his dad could help to have this reinstated, although this has been dismissed as "wholly inaccurate" by a palace source.

And now a friend of Harry's told the magazine: "He gets 'unavailable right now'. His calls go unanswered. He has tried to reach out about the King's health, but those calls go unanswered too." While another friend added: "Harry is frightened and feels the only person who can do anything about it is his father," while another source added: "Harry is determined to protect his own family at all costs."

They added that the couple "didn’t feel they had a choice". "The only option was to leave - for their sanity. I do think they thought if they got out of this bubble, there would be less focus on them," the insider said.