Daniel Allen jailed for at least 29 years over Derrylin fire deaths
Daniel Sebastian Allen, 33, has been jailed for a minimum 29 years for killing three generations of the same family in County Fermanagh in February 2018.
The judge told him he would not be considered by parole commissioners for release until 2047.
Allen showed no emotion as he was led from the dock at Laganside Crown Court.
The judge told him: "There's a very dangerous and disturbing part of his makeup that led to these deaths."
Denise Gossett, 45, her son Roman, 16, his sister Sabrina, 19, and Sabrina's 15-month-old daughter Morgana Quinn died at a burnt out cottage in 2018.
Allen pleaded guilty to murdering the three youngest victims and to the manslaughter of Denise by reason of a suicide pact.
He had been living with the family.
Roman Gossett and Morgana Quinn died from GHB poisoning, a drug which has a sedative and anaesthetic effect.
Allen claimed he strangled Sabrina but there was no evidence to prove this and her cause of death could not be ascertained.
Denise Gossett was still alive when the fire started and died from smoke inhalation.
Her body was found handcuffed to a bed.
'Horrific and cruel'
In a statement read outside the court Samantha Gossett, Denise Gossett's daughter, said her mother was her "rock".
"My beautiful mother was taken from me. My younger brother and sister, Roman and Sabrina, along with Sabrina's wee baby Morgan are all gone too," she said."Their four lives were taken in a fire started deliberately. And it breaks my heart to think on what happened; to think on how they died."She added that it was "very difficult to convey such a loss in words".
Det Insp Hazel Miller described the fire as a "horrific and cruel act".
"It's hard to even begin to imagine the panic, fear and sheer suffering," she said.
"I'd like to acknowledge the efforts of our police officers and of colleagues from the Fire Service and the Ambulance Service, who attended this heart-breaking scene and tried so hard to save the family.
"I'm also keen to thank neighbours and local people for their selfless support."
Det Insp Miller said the deaths would "never be forgotten".
"We've seen destruction and a loss beyond words. My thoughts are with the remaining family members, whose lives won't ever be the same."
Daniel Allen was originally from the Midlands area of England and had met Denise online.
He initially lived with her and her family in Scotland.
They moved to Ireland, first to Tralee and then to Cavan, before renting the property in Derrylin where they lived for 14 months before the fatal fire.