Truss to move teenage daughters and husband into Number 10
Frances and Liberty -- believed to be 16 and 13 -- will be the first teenagers to stay at the iconic address since the children of Labour leader Tony Blair in 1997.
The Times described the girls' arrival as "a concept straight out of a sitcom: a teenager, at a time of peak sass, disregard and disrespect for one's parents, growing up in Downing Street".
But Truss, 47, has so far carefully protected her daughters from any publicity.
The few photos she has posted on Instagram show them from behind: walking in school uniform or scooting in a park.
Reporters have worked out their ages from pictures of birthday cakes.
A source told The Times that Truss would continue to be "zealous in protecting their privacy".
During her Tory leadership campaign Truss said the girls, who reportedly attend state schools, were actively involved behind the scenes.
"My kids were one and four when I was elected (MP in 2010) so I always say they haven't known any different," she told the newspaper.
"I talk to them about politics all the time."
She described Frances as "maybe a bit more centrist" and Liberty as "maybe very slightly more Conservative", adding "they are both very supportive of me".
Frances worked on the digital team at the campaign headquarters after gaining a computing qualification at school, Truss told The Daily Telegraph.
Liberty "has been at quite a few campaign meetings and doesn't hesitate to offer me a lot of political advice," she added.
Liberty was spotted wearing a "Liz for leader" T-shirt at a hustings, Le Monde reported.
In August, Truss told the Daily Express that her daughters were "very excited" and Liberty "keeps asking would she be able to have sleepovers if I get into No 10".
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The girls will be the first teens living at Downing Street since Blair's term in office. He had three teenage children in situ during his 10-year stay.
Famously, the Blairs' eldest son Euan was found by police lying drunk on the pavement in central London at the age of 16.
He had moved into Downing Street aged 13.
Since then the prime ministers' offspring in residence have only been babies or pre-teens and strenuously shielded from media intrusion.
Boris Johnson's two young children with his wife Carrie -- Wilfred, aged two, and Romy, who was born in December last year -- have always been photographed from the back only.
This contrasts with the much-photographed and scrutinised early years of the children of US presidents, such as Chelsea Clinton or the Obamas' daughters Sasha and Malia.
While Truss posed with her husband outside the black door of No. 10, she has stressed the trained accountant who works in finance wants to keep a low profile.
"He's a great person, but I don't expect him to be involved in the business of government," she told The Telegraph in July.
She added her 48-year-old husband was "a fantastic support to me ... But I think it's fair to say he's never wanted to be on the front line of politics".
The couple met at a Conservative Party conference and Liverpool-born O'Leary stood unsuccessfully to become a Tory councillor.
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After marrying in 2000, they stayed together when revelations of Truss's affair with a married MP threatened to derail her career a few years later.
Truss called O'Leary "the love of my life" in an Instagram Valentine's Day post.
Friends told The Guardian that O'Leary would not want to live at Downing Street full-time and is "not going to be Denis", referring to Margaret Thatcher's ultra-loyal husband, who became a household name.