Chronically jealous alcoholic Carl Mills, 28, torched his girlfriend’s home after bombarding her with threatening texts.
Three generations of one family died in the horrific inferno in Cwmbran, south Wales, in September last year.
Mills sat emotionless as a judge at Newport Crown Court ordered that he serve a 30-year minimum term and warned he may never be released.
Moments earlier a hushed court listened to the mother of one of the victims describe how Mills had “ripped the heart out of our family”.
Grandmother Kim Buckley, 46, her daughter Kayleigh, 17, and granddaughter Kimberley, six months, all died in the blaze.
Prosecutor Gregory Bull QC read out the lengthy victim impact statement by Gwyneth Swain, the mother of Kim Buckley.
Mills was described as having a “callous disregard” for his partner, her mother and his baby daughter as they were trapped in their blazing home.
“His suspicious behaviour at the scene led Gwent Police to quickly apprehend him and their subsequent thorough investigation meant that we were able to build a very strong prosecution case,” senior crown prosecutor Nicola Rees said.
She said despite protesting his innocence throughout the trial, “the evidence of his jealous and controlling nature makes it all too clear what his intentions were”.
In court Mills had tried to pass himself off as a loving boyfriend intent on starting a family and marrying his teenage partner.
In reality he groomed Kayleigh for sex after first making contact with her on Facebook in 2010 and moving down from Manchester.
As her first love the teenager skipped school and slept rough with Mills, who tried to use his control to separate mother from daughter.
But when she became pregnant with his twins, one of whom was stillborn, he realised his influence over her was diminishing.
The arson attack in the early hours of September 18 last year came as baby Kimberley was allowed home for the first time.
The family and friends of the three victims burst into applause as trial judge Mr Justice Wyn Williams passed sentence.
Gwyneth Swain described in her victim impact statement how the murdered family were known as “the special Ks.” She described daughter Kim as her best friend, adding: “The heart has been ripped out of our family, a heart that can never be replaced.”