Mia Broadhead described her father Andrew Broadhead as "the world's greatest superhero" and her sister Kiera as "the world's brightest star" as she read out a statement at Leeds Crown Court.
Mia addressed the court during the sentencing of Daniel Jones, 29, who was found guilty of the manslaughter of Mr Broadhead and his eight-year-old daughter last month.
In a rare move, the teenager stood in the witness box and addressed the packed Courtroom One, telling the judge about her struggles to cope following the fire in October 2016, when she was 12.
But when she began to describe her father and sister she began to cry, wiping away tears and pushing her hair off her face as she continued to read out her words.
She told the court: "My daddy was the world's greatest superhero and he was my hero. I am thankful for his happiness, kindness and his love for everyone - the way he was positive and how he always lifted everybody's spirits."
Mia said of Kiera: "My sissy was the world's brightest star and nobody will dull her sparkle. I am thankful for the eight years we had with her - for her kindness, her funniness, her caring for one another and her humour. She didn't deserve this, neither of them did."
After she had finished reading out her statement, Mia returned to the public gallery where she was hugged by her mother, Sara Broadhead, who also read out a personal impact statement to the judge.
Jones, who sat in the dock wearing a light grey suit and was surrounded by prison officers, stared straight forward as the statements were read.
Not guilty of murder
The judge, Mr Justice Morris, had to give special permission for Mia even to be in the courtroom, as the usual age limit is 14 in the Crown Court.
Mr and Mrs Broadhead and their two daughters were asleep in their home in Wakefield, West Yorkshire, in the early hours of October 19 last year when Jones poured petrol through their front door letterbox and set it alight.
Mrs Broadhead and Mia managed to escape, but Mr Broadhead, 42, and Kiera were overcome by the rapidly spreading smoke and fire and were later pronounced dead at the scene in Ash Crescent, Stanley.
The jury heard how Jones was worried that CCTV footage from the home would reveal a raid he carried out three days earlier.
In October a jury found him not guilty of two counts of murder but guilty of two counts of manslaughter.
Debt-ridden Jones stole a safe from a friend's house in Ash Crescent in the early hours of October 16, the court was told.
The friend quickly became suspicious that Jones was the culprit and invited him to his address on the evening of October 18.
Jones was challenged about the theft and denied it but was then told that CCTV in the neighbourhood, including the Broadhead family home, could have caught him in the act.
It later turned out the camera was not even working properly.
Jones's friend told him the Broadheads were on holiday and due back in a few days.
But that information was incorrect and the family returned home earlier on October 18, jurors heard.
Jones, of Spawd Bone Lane, Knottingley, will be sentenced on Thursday afternoon.