Theirs is a tale of two very different childhoods.
On one hand, you have King Charles who was just five when his mother ascended the throne. Duty took her across the globe, leaving her sensitive first-born at home, pining for his parents.
On the other, there's Prince Andrew - a colourful character prone to misjudgement who is nevertheless said to have been adored by the Queen.
With almost a decade between them, whereas Charles' childhood had been filled with loneliness and longing, by the time Andrew, 63, and Edward, 58, had arrived, the Queen made a deliberate effort to be a more hands-on mother.
And that is said to have been a source of great jealousy for Charles, who by his own admission craved her attention.
Having seen what her sister Princess Margaret went through as a 'spare', the late monarch also apparently made allowances for Andrew, giving him freedoms that were beyond Charles' reach.
On Andrew's side, it is Charles' status and position that he is said to have craved.
Indeed, appearing on Channel 5 documentary, Paxman on the Queen's Children, Royal correspondent Richard Kay claimed Charles once said, "The trouble with my brother Andrew is that he wants to be me."
Such is the level of resentment that Andrew allegedly 'lobbied hard' for the crown to skip his big brother altogether and go straight to Prince William.
A source quoted by royal expert Angela Levin in her new book, Camilla, Duchess of Cornwall: From Outcast to Queen Consort, as shared by The Telegraph, claimed that Andrew tried to persuade the Queen to stop Charles from marrying Camilla by being "quite poisonous, mean, unhelpful and very nasty," about his mistress-turned-bride.
The same royal source claimed that Diana and Andrew's wife Sarah Ferguson even "plotted with Andrew to try to push Prince Charles aside" so that Andrew could become Regent to Prince William, who was a teenager at the time.
His behaviour was said to have been, "very, very negative and extremely unpleasant" for the Queen, who disagreed with him, and it marked a rare occasion where Andrew didn't get what he wanted.
And as the years rolled by, tensions only grew.
Charles apparently sparked outrage in the York household when he excluded Andrew and his daughters, Princess Beatrice and Eugenie, from the balcony at Buckingham Palace after the Diamond Jubilee in 2012 amid his plans for a slimmed-down monarchy.
The move came just a year after he stripped his nieces of their royal protection.
He is also said to have despaired over his younger sibling's poor judgement which has seen him make friends with the family of Libyan dictator Colonel Gaddafi, and earn the unflattering title of Airmiles Andy after racking up £260,000 in travel expenses while serving as trade ambassador.
In 2018, Camilla skipped Princess Eugenie's wedding as she was 'entertaining guests' at her Scottish home - a move many interpreted as a public snub.
And in March 2019 Andrew was a no-show at Charles' big bash to celebrate the 50th anniversary of his investiture as Prince of Wales.
Princess Anne was there, while Prince Edward was unable to make it as he was officiating an event for the Duke of Edinburgh award program.
And a palace source mysteriously claimed that Andrew had a 'private engagement', reportedly refusing to confirm if he had been invited or not.
At the time, his non-attendance was described as a "a naked display of hostility" to the Daily Beast.
"It is pretty extraordinary. One hears tales of tension between the brothers, but the more you reflect on this, the more peculiar it seems," a source said.
The Queen reportedly harboured a great sadness over Charles' distance from his siblings.
"The Queen just says, 'Well, there is nothing you can do about Charles," a second source claimed. "What is she supposed to say? 'Like your brother more?' She doesn't intercede. That's not her style."
Now, with the Queen gone, relations show no signs of thawing.
Determined to streamline the monarchy and make big cost savings, Charles has reportedly stopped Andrew's £249,000-a-year allowance, making it difficult for him to stay in his current £30million home, the Royal Lodge in Windsor.
Instead, his brother has offered him Harry and Meghan's old home, Frogmore Cottage, which while luxurious is a world a way from the opulence Andrew is used to.
Charles is said to have been instrumental in Andrew's banishment from official royal duties following his secret out-of-court settlement with Virginia Giuffre, who alleged she was forced by Jeffrey Epstein and Maxwell to have sex with the Duke on three occasions after being trafficked by the pair. Prince Andrew has always denied the claims.
And now there's a fresh row about Charles' plan to ban Andrew from wearing ceremonial robes at his coronation.
As reported by The Mirror, King Charles is torn over whether to allow his disgraced brother to don the theatrical regalia after Andrew was forced to step back from royal duties following a sex abuse scandal.
The King’s coronation on May 6 will be a designated “Collar Day” meaning members of the Order of the Garter, the oldest and most senior Order of Chivalry in Britain, may wear the regalia and collar that signifies the British orders of knighthood they belong to.
Andrew now faces being ordered to wear a lounge suit after he was stripped of his military appointment Colonel of the Grenadier Guards, although he remains a Vice Admiral because of his service in the Royal Navy.
