KEY POINTS:
In his Marxist critique of Western politics, The State in Capitalist Society, the late Ralph Miliband, left-wing academic and author, aimed to show that "the pluralist-democratic view of society, of politics and of the state in regard to the countries of advanced capitalism is in all essentials wrong".
When he wrote those words in 1968, one of his sons was 3; the other would be born the following year.
For all his skills as a sociologist, it's unlikely Miliband ever imagined his boys would grow up to assume key roles at the very heart of the democratic state of which he was such an implacable critic.
Last week, the Milibands became the first brothers to be simultaneous British Cabinet members since Oliver and Edward Stanley in 1938, Ed being promoted to Cabinet Office Minister and Chancellor of the Duchy of Lancaster, and David becoming the youngest Foreign Secretary since David Owen in 1977.
They have consistently played down their upbringing, though it is known that they were very close to their father, who died in 1994.
Ralph was born Adolphe Miliband in Brussels, the son of Polish-Jewish emigres. He became a refugee in 1940 when he managed to evade the Nazis and catch the last boat to England.
Like many from his generation, a commitment to anti-fascism involved a socialist stance against capitalism.
The Miliband house in Primrose Hill - an area as comfortable as it sounds - in North London was a meeting place of the "new left", the group of intellectuals that formed around the New Left Review, as well as more traditionalist Labourites and communists. The writer Tariq Ali and former Labour minister Tony Benn, for example, were regular visitors.
In his diaries, Benn says of Miliband's funeral: "Anyone on the real left of any significance was there."
There is a story that when David was a schoolboy, studying at home alone, he answered the door to Joe Slovo, then head of the African National Congress' military wing.
Unflustered, he spent the next hour chatting to the man the South African apartheid regime had repeatedly tried to assassinate.
Yet rather like their Cabinet colleague Hilary Benn, the Miliband brothers rejected a left-wing path that had begun increasingly to resemble a cul-de-sac. Benn also writes in his diaries that Miliband snr, who was a close friend, confided that his sons complained to him about his idealism.
"Oh, Dad, how would you do that? Would it work? What are your positive proposals?" Benn tells him that it's the same with his sons.
"He was very relieved to hear that," Benn writes. "I think he thought he was out of date."
One reason the Milibands may have taken a more pragmatic approach to politics is the experience of seeing close up how left-wing ideas didn't necessarily produce the best results.
They both attended state-run Haverstock comprehensive school in North London, which then drew a number of children from the Primrose Hill intelligentsia, although it was made up mostly of working-class kids from Kentish Town and Camden.
Novelist Zoe Heller, whose book Notes on a Scandal was set in a school that resembled Haverstock, was David's classmate and academic rival. He kept his school essays and recently he noticed a teacher's comment on one of them: "Very good, but if you want to see how it should be done, take a look at Zoe's."
Heller remembers that David and Ed were referred to as the "brilliant Miliband brothers". At 17, she and David took part in a radio discussion on the Falklands conflict. "He was measured, funny, articulate. I realised then he was quite exceptional."
Haverstock was a poorly run and ill-disciplined school that was scrupulous only in discouraging competition and academic excellence.
Its success in this respect can be measured by the fact that David, whom Alastair Campbell, Tony Blair's publicity manager, famously dubbed "Brains", managed only to get three Bs and a D in his A-levels. Despite his mediocre grades, he went to Oxford, as did his brother four years later, both of them to read politics, philosophy and economics. At university, the brothers' serious and studious characters emerged in full.
They both worked hard and got involved in student politics. As would later prove the case in Westminster, Ed seemed the more approachable and down to Earth.
David once described his brother as "more clubbable, more handsome". This may be a case of undeserved modesty. Not long ago, a table full of women's magazine editors swooned after a meeting with David.
Some have suggested Ed is even brainier than Brains. Certainly, he seems to possess the endearing quality of not wishing to appear too clever.
David went to Massachusetts Institute of Technology after Oxford and Ed to the London School of Economics. Both brothers had brief stints in civilian employment, David working for the National Council for Voluntary Organisations, while Ed tried current affairs television.
That lasted until he interviewed Harriet Harman, then a shadow Cabinet member, who offered him a job as a speechwriter and researcher. In turn, he was nabbed by Gordon Brown, with whom he gained a reputation as a smart number-cruncher who could parlay figures into policy.
Meanwhile, David, after proving himself as a natural wonk at the Institute for Public Policy Research in London, became Tony Blair's head of policy.
Both brothers were rewarded with safe seats, David in 2001 with South Shields and Ed four years later with Doncaster North.
They were similarly fast-tracked into government. One observer said that David has not managed to bond with his constituency party. But Alan Donnelly, the chairman of South Shields' Labour Party, claims that while Miliband is "quite a shy person", he is well-liked by local activists.
If there has been talk for a number of years about the considerable potential of the brothers, it's fair to say the talent has so far failed to capture the public's imagination.
Last year, Blair jokingly suggested that David was the "Wayne Rooney in the Cabinet". It's known that Blair was on the point of giving David the job of Foreign Secretary in that year's Cabinet reshuffle, only to suffer a failure of heart at the last moment, when he opted for Margaret Beckett.
Some political analysts speculate that had he installed Miliband at the Foreign Office, then Blair might still be Prime Minister. The theory goes that Miliband would not have been as compliant as Beckett during the Lebanon crisis, which created the critical momentum that effectively unseated Blair.
It's an intriguing if futile question which takes as answered a great unknown: is David Miliband tough? And how will he respond when the heat is really on?
THE SIBLING LOWDOWN
Born: David: July 15, 1965; Ed: December 24, 1969. (Father Ralph, born January 7, 1924, died May 21, 1994). Both educated at Haverstock Comprehensive and Oxford University. David is married to violinist Louise Shackelton with one adopted child.
Best of times: Now. The first brothers to be simultaneous Cabinet members since Oliver and Edward Stanley in 1938.
Worst of times: Not much so far. If one were straining, perhaps, for David, the weeks of uncertainty before he decided not to run as a leadership challenge to Gordon Brown.
WHAT THEY SAY
David: "Gordon is the best qualified and will be the best Prime Minister and the best leader of the party."
Ed: "For globalisation to continue to command public support, we need an answer to the people who worry about competition for low-wage jobs driving down earnings."
WHAT OTHERS SAY
Of David: "He has the brain the size of a planet. But he's barely known outside of Britain - that could either work for him or be a real problem." - Alex Bingham of the Foreign Policy Centre think-tank.
Of Ed: "He's certainly a gamble. But he could prove to be a gamble that pays off." - Julian Astle, director of the Centre Forum.
- OBSERVER
