Will Harry fly back to see the sister-in-law he was once so close to? Duke of Sussex - who was affectionately treated like a younger brother by the Princess of Wales - faces another flight back to Britain as his family is thrown into new health crisis

It remains to be seen whether Prince Harry will fly back to the UK to be with the Princess of Wales after she announced her shock cancer diagnosis. 

The Duke of Sussex, 39, described Kate as the 'big sister I never had' when she became engaged to William 11 years ago, but their relationship has fractured following the bitter aftermath of Megxit. 

Harry returned almost immediately to London last month when his father King Charles phoned him to inform his son about his own cancer diagnosis, before the pair had a brief meeting at Clarence House. 

Kate, 41, last met Harry in September 2022, when they joined their spouses on a surprise walkabout at Windsor following the death of Queen Elizabeth II. 

Supporters of the Royal Family will hope Kate's health problems could prompt a reconciliation between the warring couples - but this seems a distant dream. 

The Princess of Wales and Prince Harry at the Anzac Day Service at Westminster Abbey in London on April 25, 2019

Kate and Harry last met during commemorations in London following the Queen's death in September 2022. They are seen on a surprise joint walkabout in Windsor 

Kate started dating William in 2003, after meeting him at the University of St Andrews. Soon after, she met Harry and the two grew close (pictured, in 2012) 

Kate announced tonight that she has been diagnosed with cancer and is undergoing 'preventative' chemotherapy.

She revealed the news in a deeply emotional public statement today, which paid tribute to William and her children, George, Charlotte and Louis.

She asked for 'time, space and privacy' while she completes her treatment. 

It comes at a difficult time for the Royal Family, with Charles still undergoing cancer treatment and Sarah, the Duchess of York, being diagnosed with skin cancer in January. 

Harry's decision about whether to fly to the UK from Montecito to be with Kate is likely to be heavily influenced by the kind of welcome he expects to receive. 

In his memoir Spare, Harry described hearing about William and Kate's engagement in November 2010 and saying how he would take her under his wing, 'or she'll be taking me under her wing probably'.

The personal bond between the pair appeared to grow after the marriage. 

A 2016 report by Daily Mail detailed how when Harry was in the Army, he visited William and Kate in Anglesey, in their five-bedroom rented farmhouse on Sir George and Lady Meyrick's estate.

There, the trio enjoyed local pubs, high teas and hearty suppers after long walks on Anglesey beaches away from the public eye.

A 'strong, sisterly bond was cemented with the at-times lonely Harry', a source said. 

Harry met Meghan in 2016, with the two immediately growing close. 

In Spare, Harry recounted telling Kate and William how it had been his 'dream for a long time' to become 'a foursome.'

However he claimed William told him 'it may not happen' and that he would 'have to settle'. 

Years before Kate and William got married, she spent time growing close to Prince Harry (pictured attending a concert for Diana in 2007) 

Prince Harry said he was 'delighted' about the engagement of Prince William and Kate Middleton following the announcement in November 2010 - and said the marriage meant he was 'gaining a sister he had never had' 

The pair laugh together while attending Trooping the Colour in 2014  

Kate, Harry and William take part in welly wangling with children and representatives from charities and Aardman Animations

Harry proposed to Meghan in 2017, saying, 'I knew she was the one from the very first day', during a photocall in the Kensington Palace gardens.

Kate and William said they were delighted, with an official statement reading: 'We are very excited for Harry and Meghan.

'It has been wonderful getting to know Meghan and to see how happy she and Harry are together.'

Meghan quickly joined the former trio at royal engagements, taking part in her first official appearance with the trio in February 2018.

William, Kate, Harry and Meghan's joint venture was intended to harness the star power of the four high-profile royals.

They were dubbed the Fab Four after taking to the stage together at the first - and so far only - Royal Foundation forum in London.

At the time, Harry said 'working as a family does have its challenges', but insisted 'we're stuck together for the rest of our lives'. 

The royal trio launching Heads Together, a mental health initiative  

The threesome raise their wands on the set used to depict Diagon Alley in the Harry Potter Films in 2013 

The trio took part in a relay race, during a training event to promote the charity Heads Together, at the Queen Elizabeth Olympic Park in London, on February 5, 2017

Kate and William at the Heads Together event on February 5, 2017 

However, shortly after the wedding, reports began to circulate that there had been a disagreement between Kate and Meghan over bridesmaids dresses, which had ended with Meghan crying.  

Amongst growing rumours of a feud between the two couples, they announced plans to split households and that Meghan and Harry would move out of London to Windsor. 

In January 2020, the Duke and Duchess announced they intended to step back from their roles as working royals.

Sources said at the time that Kate 'missed' her close bond with Prince Harry and worried she'd 'never be close to him again.'

According to an insider, the Princess had been left crying over the distance between herself and her brother-in-law.

Meghan joined the family for Christmas in Sandringham in 2017, but rumours of tension between the brothers was already growing 

In February 2018, the trio officially relaunched as a foursome for their first annual Royal Foundation Forum - however it became the only time the event occurred 

Prince William acted as best man at Prince Harry and Meghan's wedding - but there were rumours of tensions in the months before the big day 

By November 2018, it was reported Prince Harry 'felt William wasn't rolling out the red carpet for Meghan and told him so'  

'She wishes she could speak to Harry,' the source told Us Weekly. 'She misses him and fears she'll never be close to him again.'

Kate last met Harry after the Queen's death in September 2022, when they joined their spouses on a walkabout in Windsor.

However throughout the rest of the walkabout, which is believed to have lasted some 30 minutes, Prince William and Kate, and Meghan and Harry, appeared to stick to their two couples - perhaps instructed to by their aides - and barely interacted during the sombre occasion.

All evidence suggests the relationship between Kate and Harry remains extremely strained to this day. Only time will tell whether Kate's health problems may go some way to healing it.

That Christmas, the foursome put rumours of a rift to one side when they stepped out at Sandringham together 

In January 2020, the Duke and Duchess announced they intended to step back from their roles as working royals. They made their final appearance in March 2020, at a frosty Commonwealth Service