Arthur Simpson-Kent, 49, has pleaded guilty at the Old Bailey to the murder of his partner, former EastEnders actress Sian Blake, and their two children.
Blake, 43, disappeared on December 13 along with her sons Zachary, eight and Amon, four.
Their bodies were found buried in the garden of their home in Erith, in south east London, on 5 January.
Simpson-Kent vanished days after their disappearance and was tracked down to Ghana. Simpson-Kent was extradited back to the UK and arrested on his arrival.
Wearing a red T-shirt and black trousers, he appeared via video link from Belmarsh jail.
He was remanded in custody ahead of a three-day sentencing from October 4.
Outside court, Blake's sister Ava smiled and said the family were "really relieved".
Police had spoken to Simpson-Kent, a former model turned hairdresser, after his partner and children disappeared on December 16, three days after they vanished and two days before he fled the country.
He was reportedly eating a coconut on a beach when he was arrested in Ghana after he was “smoked from a thicket” where he had been hiding and arrested by armed police
At an earlier hearing, Mr Justice Singh was told Simpson-Kent admitted to the killings, though he did not enter a plea until Friday's hearing.
Blake played the character of Frankie Pierre in 56 episodes of EastEnders in 1996 and 1997.
She had motor neurone disease before she died.
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