TO an only child, sibling rivalry is a mythical, fascinating beast.

They mess you up, your mum and dad, to paraphrase the poem, but a lot less is said about the emotional intricacies of brothers and sisters, and how these relationships shape the psyche.

If it's bad enough for your average weans, imagine the added stressor of birth order dictating your future choices, your fortune and how everyone in your life responds to you.

So the revelation from a leaked copy of Prince Harry's new biography that Prince William and he came to physical blows in a row over Harry's wife is not of huge surprise, despite the shock-horror reporting from some quarters of the media.

In my experience of childminding for friends' pairs of sons, small boys find it difficult to keep their hands off one another. And their feet and their fists and their elbows. They tend, I believe, to grow out of it but it's tiresome at the time and must be nigh-on unendurable for the parents if it persists.

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You'd hope grown men might be able to solve their disputes without fisticuffs, particularly when one of those men is the future king, but status and responsibility become nothing when sibling passions take hold.

King Charles, in the leaked extract from the book, is reported by his younger son to have said, "Please, boys, don’t make my final years a misery." If their great wealth and general remoteness make it difficult to meaningfully relate to the royal family, this soap opera-esque line must resonate to any parent with sparring children.

Despite the wealth and power and privilege it is easy to see the very human responses playing out in the ongoing saga of Harry and Meghan and their split from the royal family.

It all seems utterly hellish, the detail so far from Prince Harry's misery memoir, detailing a lost boy looking for love and the acceptance of his family.

Meghan is not strictly an only child but is the only child of her mother and was not raised in the same household as her older half-siblings, so one imagines she would like the experience of cousins and a busy extended family for her own brood.

This, the effect on the youngest members of the royal family, makes the estrangement all the more sad. You feel desperately sorry for all involved.

But how long are those with sympathy for the Duke and Duchess of Sussex supposed to carry on feeling warmly towards them as the parade of revelations continue?

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There are some vignettes revealed that give an insight into what made Prince Harry the man he is. An account of a tawdry loss of his virginity, a pragmatic take on the men he killed while stationed in Afghanistan. Harry also details going to speak to a woman with "powers" – he avoids saying medium or psychic – in order to be connected to Princess Diana, a boy chasing a ghost.

One story recounts a falling out over Meghan commenting on Kate Middleton's "baby brain" and William putting her in her place, saying she's not close enough to her sister-in-law to comment on her hormones. Jeezo. It seems a lot of priggish self-importance from William and Kate but this is a family that still insists on curtseying to one another behind closed doors.

Parents say terrible things because parents are human. In his reporting of events, Harry says his father told his mother she'd provided a "spare" on the day of his birth. That he came second by pure accident of birth seems an indelible sting to Harry, despite the fact that pure accident of birth has left him still very, very fortunate indeed.

The freedoms Harry enjoys must seem tantalising to William. The responsibility of being the oldest must be a grim and gruesome thing in many regards, particularly given the diminishing popularity of the royal family and the dwindling automatic deference the royals enjoy. This will continue to shrink under King Charles and then, when the day comes, under William.

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No one wants to be the prime minister under which the United Kingdom is divided and no one wants to be the king under which the monarchy crumbles. What a burden to bear and to be at loggerheads with one of the vanishingly few people who know that burden must be awful.

Harry has clearly felt for some time that the relationships are fractured beyond repair and has decided to go hard or go home. From the images of the brothers' clear fondness for one another as they waited at the alter in St George's Chapel to this mess, now, a mere four years later. Willy and Harold, as it's revealed they call one another, seem a duo unlikely to be reunited.

The book has been leaked to the Guardian, Harry has recorded pre-publicity interviews, and there has been a concerted publicity push around the whole thing. Plenty of people trade on their personal misery for fame, as Harry is doing, but the prince already had fame and he already had fortune.

It's beginning to seem like he has nothing else to offer by way of career than monetising personal grievance.

The royal family's desire for privacy was always a front. Leaks and counter-leaks have been the tactic used to present a semblance of dignity while also exerting some control over the narrative. Harry and Meghan have been clear in their stated aim of wresting back control of this narrative.

Yet the Sussexes have reached a tipping point. The most persuasive defence for maintaining a royal family is the soft power wielded abroad and that is reason enough for Harry and Meghan's situation to be of public interest – the impression it gives of an integral British institution.

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Their complaints so far have raised questions that are in the public interest – around race, monarchy and the media.

We'll never know the truth of what really happened among the family because we were not there. And truth is entirely subjective, even – often especially – for those there.

Without the important questions raised, this moves from being a dispute in the public interest to a private family affair, dirty laundry being aired for all to see. It's become EastEnders with crowns on, a Shakespearean tragi-comedy in real time.

As sympathy turns to scorn, another relationship may become just as difficult to resolve: that increasingly distant link between the royals and the public.