If Labour wants to convince disaffected voters that its politicians aren’t drawn from a narrow, self-serving Westminster elite, it has a few problems. The latest research found that 54 per cent of the party’s candidates selected in marginal or inherited seats (those with retiring MPs from the same party) for 2015 have already worked in politics or for think tanks. In comparison, 17 per cent of Conservative candidates are political insiders.

There’s another reason why Labour politicians might seem hard to tell apart. Let’s start with Aberavon, a constituency in south Wales that has voted Labour since the 1920s. There is little to tie Labour’s candidate to this safe seat. When not knocking on doors in Wales, he splits his time between Mayfair, where he works as a business adviser, and Denmark, where his wife, Helle Thorning-Schmidt, is prime minister. There’s a lot tying Stephen Kinnock to Labour, however. His father is the former party leader Neil Kinnock and his mother is Glenys Kinnock, the erstwhile Labour MEP.

Or take Labour’s hopeful in Rossendale and Darwen, Will Straw. His father, Jack, a former home secretary, has held the neighbouring constituency of Blackburn since 1979. David Prescott, son of the former deputy prime minister John Prescott, has had less luck, having made three failed attempts at Labour candidacy. But in May, Joe Dromey, son of Jack Dromey MP and the deputy Labour leader, Harriet Harman, was elected a Labour councillor in New Cross, London. The decision by Euan Blair, Tony’s eldest, to quit his job at the investment bank Morgan Stanley in London in 2012 and move to a recruitment firm in Coventry suggests that he, too, might fancy a career in politics.

Labour’s so-called Red Princes have all worked in politics – in think tanks, for the European Parliament or US Congress, or as campaign strategists. Neil Kinnock is the son of a coal miner and Jack Straw grew up on an Essex council estate but their offspring enjoyed affluent upbringings and effortless transitions from Oxbridge into high-flying jobs. What does this tell us about the state of the Labour Party – or even British democracy?

The House of Commons is a close-knit, domestic place. One in 12 MPs is related to another current or former MP. As inexplicable as it may seem to the electorate, sometimes politicians fall in love with each other: 14 MPs are married to current or former MPs. This leaves 22 children of MPs, 11 grandchildren and a smattering of cousins, nephews, nieces, great-nephews and great-nieces. Three MPs are the third generation of parliamentarians in their direct family (Labour’s Hilary Benn and the Tories Nicholas Soames and Nick Hurd, son of the former foreign secretary Douglas Hurd).

Political families are curiously common in democracies across the world. In 2013, Justin Trudeau became the leader of Canada’s Liberal Party. He is the son of Pierre Trudeau, who was prime minister between 1968 and 1984 (with a break in 1979-80). Also in 2013 South Korea voted in its first female president, Park Geun-hye, daughter of Park Chung-hee, the country’s authoritarian leader from 1961 until his assassination in 1979.

America’s founding fathers opposed inherited power but the son of John Adams, the second US president, went on to become the sixth president, and since then the Bush, Kennedy, Roosevelt, Clinton and Rockefeller clans have dominated modern state and federal politics.

Five years ago, the US-based economists Ernesto Dal Bó, Pedro Dal Bó and Jason Snyder published a study of American political dynasties in the Review of Economic Studies. They found that since 1966, roughly 7 per cent of US legislators have been related to other congressmen or senators (a smaller proportion than in the UK). Their analysis aimed to debunk a few convenient myths about political families.

First, are the children of politicians simply more likely to inherit political talent? Not if the Review of Economic Studies findings are anything to go by. When a congressman or congresswoman holds power for more than one term, this doubles the probability that one of their relatives will enter Congress. In the words of the authors: “Political power . . .

begets power.” Labour’s Red Princes can’t put their success down to superior social-democratic DNA.

Or perhaps it was natural for Straw, Prescott, Dromey and Kinnock to follow in their parents’ footsteps. The authors found that 10 per cent of lawyers in the US have fathers who do the same job, as do 14 per cent of carpenters and doctors (but just 1.5 per cent of economists). Yet, once you account for the relative size of these professions, politics emerges as by far the most dynastic. A GP’s child wanting to become a medic is striving to join a workforce of about 150,000 NHS doctors, while an MP’s son or daughter is hoping to take up one of just 650 seats in the Commons. That 22 have succeeded suggests that having a parent in politics is a big advantage.

So what do the Red Princes have over the rest of us? The Institute for Government estimates that it costs £41,000 over four years to become a parliamentary candidate. This is a lot but nothing compared to the $1.7m that American candidates need to raise for a seat in the House, or roughly $10m for one in the Senate. US candidates need to be good fundraisers; in the UK, it’s more important to ingratiate yourself with the party leadership.

So if you felt like being kind, you could say that Labour’s Red Princes have benefited from “high social capital”, but perhaps you would prefer the term “nepotism”. The children of MPs enter politics with an understanding of the Westminster system, as well as ready-made political connections and influential backers, which all help if you are looking for a parachute into a winnable seat.

In this way, at least, Labour reflects the society it aspires to represent: the UK has the lowest level of social mobility in the developed world. A 2011 survey by the recruitment agency Aldi found that over a third of Britons were not even interviewed for their job, having been recommended by a friend or relative. Politics, because it involves the trading of favours and the formation of alliances, lends itself quite naturally to nepotism – which might be why top-down attempts to tackle the problem have been so embarrassing. Last year, it emerged that the government’s anti-nepotism tsar, the Dragons’ Den entrepreneur James Caan, had given jobs to two of his own children.

For Labour, this is a problem. How does a party of political princelings and Westminster insiders convince anyone it can represent the working classes? Opening Labour up to less privileged candidates will require decisive reform.

Editor’s note, 16 December: David Prescott has been selected as Labour’s candidate for Gainsborough