Duwayne Philpott, aged 13, died overnight in the Birmingham Children’s Hospital with his parents at his bedside, Derbyshire Police said.
His sister Jade, 10, and brothers John, nine, Jack, seven, Jessie, six, and five-year-old Jayden.all perished in the blaze at the house in Victory Road in Allenton, Derby, in the early hours of Friday.
Assistant Chief Constable Steve Cotterill said: “I am sad to confirm the news that Duwayne has died as a result of the injuries he suffered in the fire.
“My deepest sympathies go out to Mr and Mrs Philpott at this distressing time.
“The family has asked for privacy as they come to terms with the events of Friday and the loss of their children.”
A spokesman from Birmingham Children’s Hospital said: “Despite the intensive care team’s greatest efforts, the injuries that Duwayne received in the fire were too great for him to survive.
“Our thoughts are with his family at this difficult time.”
The children were asleep in their beds upstairs when the fire broke out at the semi-detached house in the early hours of the morning.
The children’s father, Mick Philpott, made a “valiant” attempt to save them, police said.
A 28-year-old woman and 38-year-old man, both from Derby, were arrested by officers investigating the deaths but were yesterday released without charge. Police said they were still treating the fire as suspicious.
Mr Cotterill added: “This investigation is still at an early stage and it should be stressed that we have not yet had the opportunity to speak to Mr and Mrs Philpott properly because they’ve been caring for their son in Birmingham.
“I want to thank the local community who have already come forward but I would urge anyone with any information, regardless of how insignificant you think it may be, to contact us.
“We would specifically like to speak to anyone who was in or around Victory Road between 3am and 4am on Friday morning.”
Said to be the father of 17 children, Mr Philpott hit the headlines after demanding a larger house to share with his wife Mairead, girlfriend Lisa, and eight offspring.
He was dubbed “Shameless Mick” in 2007 for his benefit claims and refusal to get a job in a TV documentary by former Conservative MP Ann Widdecombe.
Mr Philpott is reported to have demanded the bigger property because his council house was too cramped to accommodate the family. He wanted the city council to rehouse them, but the authority said they already had the biggest available council property in the city.
Ms Widdecombe, who spent a week living with the then 57-year-old Philpott for the programme, Ann Widdecombe Versus The Benefit Culture, said following the tragedy: “Nobody would ever call him a bad father. I’m so sorry to hear the news and my thoughts are with the family.”
Locals on the estate where the smoke-blackened house stands said they had set up an online charity since the children’s deaths to help the family with funeral costs and anything else they may need.
Over the weekend a number of special church services were held for the children at St George’s Roman Catholic Church and five candles were lit in their memory.
The church is affiliated with St George’s Catholic Primary School in Littleover, where the children went to school.