Two siblings building their careers in the cockpit of British politics looks like a recipe for tension and division. The nation remembers Ed Miliband successfully running against and, in the view of many, "stabbing in the back" his elder brother David Miliband in the battle for the Labour party leadership in 2010.

Jo Johnson, Boris Johnson's younger brother, was well aware of the potential pitfalls when he first entered public life as head of the Downing Street Policy unit for David Cameron in 2013. By that time his brother Boris, who is seven years older, had already been a Conservative MP for Henley and was currently the Tory Mayor of London. Jo was on the candidates list to become a Conservative MP.

Image: Boris Johnson said his family wasn't like the Miliband brothers

"So you're not like the Miliband brothers then?" Boris was asked by an Australian journalist, provoking what he called "an instant rebuke".

"Absolutely not,'' he replied. "We don't do things that way, that's a very left-wing thing... only a socialist could do that to his brother, only a socialist could regard familial ties as being so trivial as to shaft his own brother.


"I mean, unbelievable! Only lefties can think like that... they see people as discrete agents devoid of ties to society or to each other, and that's how Stalin could murder 20 million people.''

Image: Jo Johnson quit as a minister and an MP

But now Jo has delivered the most devastating blow so far to his brother's premiership, barely 40 days after accepting an offer to return to his government as a minister.

As Boris struggled with defeats in parliament and the defection or sacking for senior Conservatives for opposing his Brexit plans, Jo announced that he was quitting politics altogether - as both a minister and a member of parliament.

Jo tweeted: "It's been an honour to represent Orpington for 9 years & to serve as minister under three PMs. In recent weeks I've been torn between family loyalty and the nationals interest - it's an unresolved tension & time for others to take on my roles and MP & Minister #overandout."

Image: Many hold the view that Ed Miliband 'stabbed' elder brother David 'in the back'

Loyal to his brother, Jo resisted invitations to comment further. But the meaning of his resignation was clear. He is giving up his political career because he can no longer serve his brother because, he believes, Boris is no longer working in the "national interest".

It's the latest twist in an extraordinary family saga. The Johnson family's personal interactions reflecting the divisions in many other families licked in the national psychodrama over Brexit. This means it is worth intruding a little into the Johnson family history - few of its members are publicity shy.

Only a socialist could do that to his brother, only a socialist could regard familial ties as being so trivial as to shaft his own brother. I mean, unbelievable! Only lefties can think like that... they see people as discrete agents devoid of ties to society or to each other, and that's how Stalin could murder 20 million people.

The pater familias is Stanley Johnson. He is a 79-year-old former Conservative MEP and Brussels bureaucrat who now devotes his energies mainly to environmentalism and writing novels.

Stanley who was educated at Sherborne Public School and Exeter College Oxford has six children. Boris, Jo, Rachel and Leo with his first wife the painter Charlotte Fawcett, and Julia and Max with this current wife Jennifer.

All of them share the family's distinctive blond looks. I've encountered them socially or professionally, and I have found them, like the Miliband brothers, to be pleasant and public spirited people, although Max and Julia are not keen on the public spotlight.

Stanley was always fiercely ambitious of his children but told them that they would only get the education he wanted if they won scholarships. They mostly obeyed. Like his brother Boris, Jo went to the Britain's snootiest school, Eton, followed by the elite Oxford College, Balliol where he was also a member of the upper class Bullingdon Club.

Image: The family disagree on a lot but they don't talk each other down

So far so similar but brothers are not the same. After university their paths diverged. Boris cut a swashbuckling career as a Tory journalist, thrilling readers of the Daily Telegraph with exaggerated tales of EU excess, followed by the editorship of the Spectator, the magazine of the high Tory smart set.

Boris picked his life partners from the same social group. His second wife, the lawyer Marina Wheeler, is probably a fiercer Brexiteer than he is, while Carrie Symonds, his current partner, was chief press officer for the Conservative Party.

After a short spell in investment banking, Jo also went into journalism but for the sober Financial Times, where he was a distinguished foreign correspondent and head of the Lex column, a proving ground for high-flyers including former Conservative chancellor Nigel Lawson.

Image: Three of the four siblings are in the public eye

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Jo married the award-winning Guardian journalist Amelia Gentleman and had many friends across the spectrum, including many from the New Labour firmament.

Jo sat next to his father and brother in the QEII Conference Centre on the day this July when Boris was declared Conservative leader and prime minister. Their delight at the triumph of one of the clan was plain to see.

But the writing was already on the wall. Stanley is a pro-European, so his daughter Rachel, who has backed both the Liberal Democrats and Change UK. Rachel never hides her opinions as a regular panellist on Sky News' The Pledge but she never criticises her brother.

Even so something was bound to give in the solidarity of the Family Johnson. And now it has.

Sky Views is a series of comment pieces by Sky News editors and correspondents, published every morning.

Previously on Sky Views: Ian King - Is the chancellor's £13.8bn spending splurge a pre-election bribe? Let's hope so