By Iain Watson
BBC political correspondent
Political commentators have often talked about disputes within the Labour family. This time, that is literally true.
David and Ed Miliband were both cabinet ministers
The only two candidates for the party leadership so far are the Miliband brothers, although it is possible Ed Balls, for many years Gordon Brown's most trusted adviser will enter the fray. Taking soundings, too, is the former health secretary Andy Burnham.
Although the phrase "we'd like the widest possible contest" falls easily from the lips of virtually every Labour figure you meet, even a field apparently as wide as this has its problems.
Firstly, are the candidates distinct enough from each other? And secondly, are they distinctive enough from those who lead the new government?
All-white, all male
So far, it looks like being an all white, all male, forty-something line up. Rather like the new prime minister and new deputy prime minister in fact.
But apart from age and gender, all the putative candidates have something else in common - they were all government advisers before becoming MPs. Not unlike their leading opponents.
David Cameron was famously an adviser to the the then chancellor Norman Lamont, and Nick Clegg, while not exactly a government adviser, was an aide to Sir Leon Brittan when he was the EU's trade commissioner.
Ed Balls is thought likely to join the leadership race
Many in Labour's ranks would argue that any similarities are only skin deep. But whoever becomes leader of the opposition, they will have a potential problem in carving out a distinct political path.
When it comes to the instant analysis of what went wrong for Labour, there is a remarkable degree of consensus amongst some of those who would be leader.
Ed Miliband told the BBC: "We need to reconnect with the people we lost. We lost people who have been traditionally Labour voters over issues such as immigration."
His brother David, formally launching his campaign in South Shields said: "Labour lost the election because our conversation with the public broke down." And he said his party had been "playing catch-up on immigration and housing".
And Ed Balls, writing for the Independent, said: "People knew we had done great things... but they felt we had stopped listening. They just did not believe we were hearing their concerns on immigration, welfare, housing."
So all are agreed . A little more conversation. And action on immigration guaranteed.
But they are facing not a conventional government of the right, but a coalition of the centre-right. And one where the Lib Dems have signed up to a cap on non-EU immigration.
How they can trump this, in order to win back the trust of former Labour voters who felt the party had not done enough on the issue, while also winning over small "l" liberal voters - who believe Nick Clegg has betrayed the cause of progressive politics - will be a challenge indeed.
The centre ground which Labour had occupied is being invaded - and possibly settled - by the new government
All the candidates at least nod towards those liberal-minded voters on other issues. David Miliband believes Labour was slow on the uptake on political reform. Ed Miliband that the party was too "casual" in its attitude to civil liberties.
But they have to compete with a new government which is, with great fanfare, going to introduce a Freedom Bill to eliminate ID cards and defend trial by jury.
It has a deputy prime minister - who, after the television debates arguably has a higher media profile than some of Labour's leadership contenders - who will be in charge of political reform and will do some of the things Labour has simply talked about.
This is likely to include bringing about greater reform of the House of Lords - to make it wholly or substantially elected - and a referendum on changing the voting system.
The question is whether this will push some of the leadership hopefuls leftwards as the centre ground which Labour had occupied is being invaded - and possibly settled - by the new government.
Some have made tentative steps in that direction - Ed Miliband wants Labour to lead a "living wage" campaign - higher than the minimum wage - and is critical in retrospect of the Iraq war and its aftermath.
Labour certainly lost the support of some of those "hard working families" which just about all of their frontbench mentioned in their speeches when ministers.
But there is also a growing north/south political, rather than economic, divide - with Labour performing particularly poorly in the south of England, outside London.
And many who abandoned the Conservatives for Labour in Essex, in Kent, and along the south coast in 1997 were attracted by a New, not a traditional, Labour message.
Nonetheless there are opportunities for the next generation of would-be Labour leaders, too.
They may find willing converts among a "progressive" constituency who may like the new government's commitment to civil liberties but who may also loathe the forthcoming spending cuts.
Then the new coalition might feel the heat, and the pressure to separate, when those cuts begin to hurt - not this year, but possibly next year or the year after.
And the successful candidate will lead a party which - while losing more than 90 seats at the general election - did not melt down, and indeed which, almost unnoticed, gained seats in local government on election day.
The challenge for the aspirants will be to make sure that in their struggle for distinctiveness they do not fail to - in the jargon - "reconnect" with the voters they have just lost.