Career choices were pretty thin on the ground back in Cain and Abel's time. Still, the brothers had the good sense to choose different paths as far as they could: the first-born, Cain, tended to the arable side of the business while his sibling opted to go into livestock. Not that it did them much good.
When the time came to offer up a sacrifice, the brothers fell out in spectacular fashion. God favoured the younger over the elder, so Cain lured Abel into a field and killed him. The Bible itself is strangely silent as to the underlying reasons for the sudden animosity – jealousy over God's approval being the obvious inference (though extra-scriptural scholars cite the inevitable spectre of a rivalry over women looming somewhere in the background).
It might not quite be the oldest story in the world, but it is not far off, and anyone who has a brother will know that that relationship, perhaps above all others, is the one capable of generating the most profound feelings for both good and ill. Most of us decide from an early age that the bonds of shared parents and upbringing are more than enough to have in common, and that it is better to steer our own way through life if we want to consign the hot-eyed quarrels of our joint childhood to the past and emerge as adult individuals in our own right.
So when two brothers come to inhabit the same high-profile worlds – in politics, sport, media or music – it is hard not to wonder exactly how they prevent those atavistic emotions from bubbling up to the surface. David and Ed Miliband, who this weekend came out as rivals for the highest prize of all – to be Labour leader and possibly future Prime Minister – have dealt with the issue head on.
Perhaps hoping to reflect the coalition zeitgeist, they have gone out of their way to reaffirm their brotherly love as more important than political ambition. The younger brother, Ed, told the BBC's Andrew Marr after announcing his candidacy: "I love David, he's my best friend in life and it's been one of the hardest decisions I've ever made." For his part, big brother David described his younger sibling in glowing terms as "extremely talented" and a "great person", as well as being "someone I love very much because he's my brother". But surely it can't be quite that straightforward come the next Miliband family gathering?
Family relationship expert Dorothy Rowe, author of My Dearest Enemy, My Dangerous Friend, which examines the often contradictory aspects of sibling relationships, believes the Milibands are probably no different to most brothers in being able to cause each other both intense pleasure as well as hurt. "Even when they are friends with one another, siblings are a bit wary, and even when they are fighting they still care about each other," she says. Most psychologists agree that the great schism in any sibling relationship dates back to the arrival of the second child and the breaking of the golden period when the elder child enjoyed a monopoly on their parents' time and affection.
However the author felt that having listened to Miliband senior talking about his brother, the two have an enduring, if competitive, bond that will survive the current leadership contest. "What he (David) was describing was the sort of relationship between two brothers where they compete enormously over anything. But once it is clear who has won, or if the other brother is attacked from outside the family, then the brothers rally around and look after each other," she says. "I would guess that the two men would compete by any means available, but if one wins the leadership and the other doesn't they will support each other," she added. The most successful brothers in the public eye thrive by agreeing not to discuss each other to the media. They are also good at compartmentalising their lives. The Milibands made it an early condition that they would never be interviewed together. Friends and family are mainly sworn never to discuss the inner workings of the relationship, limiting the remarks they are occasionally authorised to make to a few positive observations.
But brothers have known, from Cain onwards, that they are saddled with each other. Rowe explains: "If you have a friend you regard as very close who you discover has treated you badly, you can feel very hurt but you can end that relationship. But other people would criticise you if you tried to end a sibling relationship. They would say 'blood is thicker than water', and it is that shared history that holds you together. That brother knows things about you no one else does."
David and Ed Miliband
Born and raised in the socialist intellectual heartland of north London, where Tony Benn dropped in for tea at the family home, David and Edward Miliband were the sons of influential left-wing academics and appeared predestined for political greatness. They attended the same local comprehensive, where they saw inequality in action, and had the same tutor when they studied at Corpus Christi College in Oxford. There Ed, the initial intellectual high-flyer, was overtaken by David, who on graduation rose swiftly through Labour ranks to become Tony Blair's chief policy wonk.
Those who know the brothers insist they have remained close. Until children arrived, they lived in neighbouring flats in the same north London house. They socialise with many of the same friends, share values and, crucially, harbour similar ambitions. Long-standing family associates insist the two remain deeply "solicitous" of each other's feelings and opinions, and say there is no evidence of bad blood between them. For his final Christmas at Chevening House, the grace-and-favour country home provided for him as Foreign Secretary, David invited his younger brother and family, along with the boys' elderly mother – who both brothers half jokingly say considers their politics to have drifted dangerously far to the right and will be supporting neither in the contest.
In the past, Miliband major has spoken, albeit slightly patronisingly, of his "gentle pride" in his younger brother's achievements. However, one anonymous source told a journalist: "There's the classic younger brother, older brother dynamic, with the younger brother a bit jealous of the older because he came first, and the older brother not seeing the younger brother quite as substantial as he is. The jealousy isn't strong but it is there."
Christopher and Peter Hitchens
Christopher Hitchens likes to joke that "the great thing about family life is that it introduces you to people you'd otherwise never meet". Yet for all the differences they so publicly espouse, it is the similarities that appear striking. Both earn their livings as journalists, though writing from opposite points on the political spectrum. Left- leaning Christopher is a feted commentator for Vanity Fair, a virulent critic of religion, and a man whose lifestyle choices, particularly when it comes to cigarettes and alcohol, long marked him out in satanic contrast to his socially conservative, highly religious younger brother.
Both Hitchens attended the same prestigious public school, though it was Peter – then even further to the left than his older brother – who chose to complete his education at the local college and then York University, rather than following Christopher to Oxford, where his brother was part of a glamorous young set including novelist Martin Amis. Yet at the heart of their most recent disagreement, which resurfaced in 2001, was a youthful comment by Christopher at the time of the 1968 invasion of Czechoslovakia, about someone who didn't care if "the Red Army waters its horses in Hendon". Peter, who had by now completed his journey from left to right, repeated his version of the remark around the time of the 9/11 attacks. His brother was furious, insisting he had merely recounted an amusing anecdote about a friend's ex-Communist father. There has been a reconciliation of sorts. They shared a platform at the Hay Festival to discuss their antipathy, but refused to shake hands and barely looked at each other. The entente between them appears practical rather than cordial.
"We're not close. We're different people, we have different lives, we have entirely different pleasures, we live in different continents. If we weren't brothers we wouldn't know each other," Peter says.
David and Jonathan Dimbleby
Two brothers born into a broadcasting dynasty, as young men they were devastated by the early death of their father, Richard Dimbleby, a distinguished war reporter and pioneer of state-occasion television commentary. Elder brother David, now aged 71, notched up his eighth consecutive general election night anchorage this year, while Jonathan, six years younger, took a break from his regular duties for ITN.
The boys, who have another brother and a sister, were both educated at Charterhouse public school. David went on to Christ Church, Oxford, while Jonathan studied at University College London. Both took to the family trade, but not before dalliances with radical politics – throwing up the bizarre sight of an anti-Vietnam demonstration at which a youthful Jonathan was a protester while David reported it for the BBC. While the older brother presents BBC1's Question Time, his younger sibling oversees the Radio 4 version of the same programme.
Their personal lives have also mirrored each other's. Both brothers' long marriages broke up when they were in their sixties, and they started relationships with much younger women before going on to have second families. Despite decades in the public eye, little is known about the inner workings of the relationship – though they remain quiet supporters of each other's endeavours. Jonathan described the situation thus: "We plough separate furrows in the same field, and therefore it is tempting to say that one wants to plough a straighter furrow than the other. I simply want to plough the straightest furrow I can. I think in any job you don't want anybody to be better than you. But when I watch my brother on an election programme, I would be really distressed if he made a major gaffe."
Noel and Liam Gallagher
They grew up together sharing a bedroom in the family home in Burnage, Manchester dreaming of being rock stars, and for nearly 20 years Noel and Liam enjoyed their fame, adulation and wealth to the full. Yet it was not the well-charted pressures of rock and roll, musical differences or a fading fan base that eventually split the Britpop superstars Oasis asunder – it was the soap opera of the Gallagher's brotherly relationship.
When it came to the final announcement it was Noel, the older, more sensible of the two, who said he could simply take it no more: "It is with some sadness and great relief to tell you that I quit Oasis tonight. I simply could not go on working with Liam a day longer." Although Oasis was formed by Liam, Noel became its songwriter and driving force. He has revealed how he was forced to put aside his feelings about his younger brother for the good of the band, aware that the volatile chemistry between the two was what made Oasis such an attractive prop-osition to many young fans, particulalrly men. One particularly violent row in 2000 meant they did not speak for five years.
Those who know them say that their families do not socialise together and for years they have only really been able to communicate with each other through the pages of the music press or via Twitter. But some believe all is not lost. Alan McGee, who signed them to his Creation record label, says he believes they will patch it up and work together again.