Boris and Jo Johnson share the family's trademark ultra competitiveness, but in many ways they are very different people.
Jo Johnson will head up the Policy Unit inside Downing Street in a shake-up to inject fresh Tory thinking into Government.
Boris Johnson has said that he is "very nervous" about playing Pippa Middleton at ping-pong after she challenged him to a match.
The Mayor of London has defended David Cameron saying the Prime Minister has not lost control of his party over Europe.
Boris Johnson said 'If you look at what's happening really, the Conservatives are the only people offering a serious renegotiation of our relationship which is what, I think, both sides want.'
But writing earlier this week in his Daily Telegraph column Mr Johnson warned Eurosceptics about leaving the EU saying that most of Britain's problems were caused by "chronic British short-termism, inadequate management, sloth, low skills, a culture of easy gratification and underinvestment."
Boris Johnson has backed Tory backbench demands for an EU referendum bill and warned David Cameron he must make clear Britain is "ready to walk away" unless its relationship is fundamentally reformed.
But the Conservative Mayor of London also issued a stark warning to eurosceptics that quitting would expose the fact that most of the country's problems were self-inflicted.
"If we left the EU, we would end this sterile debate, and we would have to recognise that most of our problems are not caused by 'Bwussels', but by chronic British short-termism, inadequate management," he wrote in his Daily Telegraph column.
"Sloth, low skills, a culture of easy gratification and underinvestment in both human and physical capital and infrastructure" also contribute to problems at home, he added, noting that British productivity compares badly to our German neighbours.
The Mayor of London Boris Johnson has criticised Lord Lawson for not allowing time for the negotiations in Europe to take place.
Speaking on LBC 97.3 radio the Conservative said London needed Europe and access to European markets.
– Boris Johnson, Mayor of London
Myself, I think it would be better to stay in the single market, to have the benefits of a customs union, the benefits of completely untrammelled free trade, rights of establishment all those kinds of things, those are very important for British business.
I think the crucial thing we need to focus on is Britain has a global future, London has a global future, we need to be in Europe, in European markets but we also need to look around the world.
The Mayor of London Boris Johnson has called on the government to rule out a third runway at Heathrow, describing the idea as "totally nuts".
Speaking to a protest in West London, Mr Johnson said that the third runway would take "at least 15 years to bring about" and was "completely impractical".
Stanley Johnson, the father of London Mayor Boris, told ITV News he was "absolutely thrilled" that his son Jo has been added to David Cameron's team in Downing Street.
He said: "I'm absolutely thrilled at this wonderful appointment David Cameron has made, there is no doubting Jo's intelligence.
"He is delighted and I'm confident the Tories will get their act together in a big way.
"I wish my father had been alive to see this and I'll keep lobbying him to make sure the Tories stay green."
David Cameron has tweeted a picture of his new policy board, which features London Mayor Boris Johnson's younger brother Jo.
The Prime Minister's tweet said: "I've been meeting with my new policy board, made up of MPs. I told them I want more ideas to help hardworking people."
The Daily Telegraph's political correspondent Peter Dominiczak has tweeted London Mayor Boris Johnson's reaction to his brother Jo heading up a Policy Unit in Downing Street.
Boris on his brother's promotion : "Great there is finally a Johnson in Number 10. Jo will be superb. Now for Rachel and Leo!"From @peterdominiczak on Twitter: