The Duke of Cambridge and the Duke of Sussex shared what appeared to be an unbreakable bond.
Their experience of a royal childhood and the trauma of losing their mother Diana, Princess of Wales, bound them together through their teens, and well into adulthood.
But the royal brothers have faced a turbulent time due to a rift that would at one stage have seemed unimaginable.
Harry, in his ITV documentary during his Africa tour, told of how he and William had “good days” and “bad days” in their relationship.
He spoke of how they were “on different paths” but told how he still loved his brother dearly.
Broadcaster Tom Bradby, a friend of the Duke and Duchess of Sussex who interviewed them for the Africa documentary, wrote in The Sunday Times of Harry and Meghan’s relationship with the royal family: “The fallout began at the time of the wedding in 2018.
“Really damaging things were said and done.
“The atmosphere soured hard and early, but few meaningful attempts were made by anyone to heal the wounds.”
He added: “There is no doubt Harry and Meghan feel they have been driven out.”
Bradby, speaking on ITV’s Good Morning Britain earlier this week, had said: “There are lots of people who would, including I think the brothers themselves, love them to be closer again.”
He described it as a “family dispute within a family firm”.
In a joint statement on Monday, William and Harry denied a newspaper claim about their relationship which they branded “offensive and potentially harmful”.
The statement did not name the newspaper but Monday’s The Times has a front page story about the crisis, and says a source told the publication that Harry and Meghan “regarded themselves as having been pushed away by what they saw as a bullying attitude from the Duke of Cambridge”.
As well as facing the scrutiny of royal life, William and Harry both served in the military, enduring the rigours of training at Sandhurst, followed by a career, for a time, in the forces.
They played polo together, and lived close to one another at Kensington Palace, where they grew up.
Although different in character, the pair were always at ease in one another’s company, frequently making jokes about each other’s hair at royal appearances.
Harry, more open and outspoken, was always been seen as more of the party prince compared with William.
Considered more reckless and the daredevil one, Harry’s most famous stunts have included being photographed playing strip billiards while on holiday in Las Vegas.
Future king William is seen as more cautious, and more measured in his approach.
Harry was William’s best man when he married Kate Middleton in 2011.
At the altar, it was Harry who reassured him that all was going smoothly on the big day, telling William when Kate arrived: “Right, she is here now.”
Harry’s best man speech was said to be both hilarious and touching.
He in turn asked William to do the honour when he wed Meghan Markle in 2018.
William vowed revenge for Harry’s best man speech and his own delivery was described as naughty.
Their friendship had a sadness at its roots.
The brothers had to endure losing their mother at a young age, an experience which brought them together in grief.
William and Harry were just 15 and 12 when Diana was killed in a car crash in Paris in 1997 and the brothers sought comfort from one another during their difficult teenage years.
Both have spoken of the warmth their mother showed them in childhood and how she strove to make them aware of those less fortunate than them.
In 2017, they marked the 20th anniversary of Diana’s death.
They viewed tributes left for the princess at her former home, Kensington Palace, and commissioned a statue in her memory.
When Harry turned 21, he described William as the one person on the planet with whom he could talk about everything.
“It’s amazing how close we’ve become,” Harry said.
“I mean, ever since our mother died, obviously we were close, but he is the one person on this earth who I can actually really … we can talk about anything.
“We understand each other and we give each other support.”
The brothers went on to work jointly on their Royal Foundation, striving to raise awareness surrounding mental health issues, along with other charitable work, then becoming a royal trio with the Duchess of Cambridge.
Harry, who was the spare to the heir until William and Kate had children, had settled down in recent years, concentrating on his charity work, and then marrying former Suits star Meghan.
But just 20 months after the glittering royal wedding, Harry’s role with the royal family stands on the edge of a precipice.
Harry and Meghan moved from Kensington Palace, left the Royal Foundation – their joint venture with William and Kate, blindsided the royals with statements attacking the press – and now want to step down as senior royals and become financially independent.
“There’s a lot of times that both myself and my brother wish, obviously, that we were just completely normal,” Harry confessed in 2012.
Despite their troubles, it could perhaps be William who is the only person who can fully understand what his brother is going through.