Through decades of personal and political clashes, the Johnson family seem to have maintained a remarkable bond – and as Boris is treated in intensive care, the ties with the rest of his clan are as indelible as ever.

Their ties have been tested by the most severe political storms. When the now prime minister Johnson became the face of the leave camp during the EU referendum, his siblings Rachel, Leo, and Jo passionately made the case for the UK to remain in the bloc. Rachel joined the newly formed and now defunct Change UK (she would later describe herself as a “rat that jumped on to a sinking ship”), while Jo dealt an extraordinary blow to his brother’s premiership after he quit as an MP and minister, citing an “unresolvable tension” between his family loyalty and the national interest.

In her newly released memoir, Rachel notes: “Doing what we are told not to do is a family trait.” So when the prime minister ordered the country to stay at home and practise social distancing last month in an effort to deal with the coronavirus epidemic, it probably came as no surprise that their father Stanley, a former MEP, defied him, insisting: “Yes of course I’ll go to the pub if I need to go to a pub.”

In recent days, the family has largely maintained a public silence – but they have expressed their support by other means.

Last night, on the advice of my doctor, I went into hospital for some routine tests as I’m still experiencing coronavirus symptoms. I’m in good spirits and keeping in touch with my team, as we work together to fight this virus and keep everyone safe. — Boris Johnson #StayHomeSaveLives (@BorisJohnson) April 6, 2020

All three siblings liked or retweeted Johnson’s message thanking hospital staff and tweets from well wishes from people across the political spectrum. Leo Johnson, whose recent activity on Twitter suggests he also approves of Labour’s new leader, Keir Starmer, liked a tweet by the Church of England praying for his brother’s recovery. The youngest sibling is the only one to stay out of politics, working instead for the firm PwC and appearing occasionally on BBC Radio 4.

Coronavirus patients aren’t allowed visitors, which will undoubtedly be difficult for the close-knit family, particularly for Carrie Symonds, the prime minister’s fiancee, who is seven months pregnant. The 32-year-old is currently self-isolating after experiencing coronavirus symptoms herself. She and the Johnson family received a message from the Queen on Tuesday, saying they were in her thoughts and that she wished the prime minister a full and speedy recovery.

Rachel has also publicly supported her brother’s response to the coronavirus. During last month’s appearance on ITV’s Loose Women, Rachel said: “I do support him, I think he’s doing an incredible job.

“It’s hard to see somebody carrying such a weight of responsibility but he is strong. It’s really hard up there to know they’re doing the right decisions … this could crash the economy.” She added: “These are really, really dark times.”

She was also quick to defend her father, Stanley, who was heavily criticised for saying he would ignore the government’s advice on how to avoid the coronavirus, admitting that while it was “a stupid thing to say”, her dad wasn’t trying to be “provocative”.

Rachel has long dismissed suggestions that the ideological differences within her family have resulted in any strife. She tweeted last year: “I said last night at a charity do that the family avoids the topic of Brexit, especially at meals, as we don’t want to gang up on the PM!”

In the book Just Boris: A Tale of Blond Ambition, author Sonia Purnell notes: “There is tension, yes, but little division among them. Constantly moving house meant it was nigh on impossible to form meaningful relationships with anyone else their own age, had they been urged to do so.”

In a 2005 interview with Grove Magazine, Rachel said of her siblings: “We never, ever, went to play with other children. We didn’t need friends.” Their bond has clearly survived the test of time – and political crises.