An inquest at Wakefield heard the fire started after a lighter was used to set fire paper in the bedroom five-year-old Alex Clarke shared with his eight-year-old brother William at their home on Second Avenue, Rothwell, on February 11 2018.
William told his mother Emma Clarke that Alex had used a lighter on the corner of a page in a book, which then fell on the bedroom floor, the inquest heard.
Detective sergeant Paul Kravtschuk of West Yorkshire Police, who investigated the fire, said there were no suspicious circumstances.
Assistant coroner Sarah Watson asked him: "There was no way you confirmed who and how the fire started?"
Det Sgt Kravtschuk, replied: "No there wasn't, only evidence we have heard."
William and his 10-year-old sister Jessica raised the alarm with their mother Emma.
Neighbours tried to rescue Alex in the bedroom, but were beaten back by thick smoke and intense heat.
Firefighters rescued Alex and he was taken to Leeds General Infirmary before being transferred to the Royal Manchester Children’s Hospital, where his death was confirmed just after 12pm the following day.
Reading a statement from Emma Clarke, Ms Watson said it had been a normal Sunday night at the start of a half-term holidays and the family had been playing board games and watching TV.
Mrs Clarke said in the statement: "Alex ran down, gave me a kiss and a cuddle and said I love you.
"Around 8.20pm William and Jessica ran down saying the bedroom was on fire."
Mrs Clarke wrote in the statement that William had said Alex had managed to get a lighter and had lit the corner of a book, which burned quickly and he had dropped it.
Fire investigator Jamie Lister of West Yorkshire Fire Service, said a badly fire damaged electronic gas lighter was found on a mattress in the bedroom.
Mr Lister said the cause of the fire was "most likely a cigarette lighter to something in the room, probably a book or papers."
Coroner Ms Watson: "Would you say it's more likely than not that it had been deliberate ignition by a lighter."
Mr Lister replied: "Yes."
Recording a verdict of misadventure, Ms Watson said : "I find that a naked flame was deliberately produced from a gas lighter. It was applied to paper."
Reading a statement from neighbour Simon Horner, who tried to rescue Alex, coroner Ms Watson said: "He ran upstairs and into a wall of black smoke and could feel intense heat coming through the walls."
Another neighbour, Krzysztof Olejnik, went into the room where the fire was and searched it, before going to the kitchen and filling pans with water, the inquest heard.
Forensic pathologist Dr Michael Parsons conducted the post mortem and concluded Alex died as as result of complications after suffering severe burns and smoke inhalation in a house fire.
After the tragedy, The headteacher at Alex’s school added his voice to the tributes to the much-loved youngster.
Oulton Primary School headteacher Richard Horton said: “He was a hardworking and friendly boy with a great sense of fun.
"Alex is going to be greatly missed by all at Oulton Primary School and we would like to express our heartfelt condolences and sympathy to Alex’s family and friends.”