The parents of two boys who were critically injured in a house fire have been left heartbroken after their youngest son passed away.
The horrific incident destroyed the Mongoo family's home last Thursday in Geraldton, Western Australia, with the brothers and a friend rushed to Perth's Children Hospital in a critical condition following the blaze.
13-year-old Nulla Mongoo suffered severe burns to 90 per cent of his body, passing away from his injuries at Perth Children's Hospital on Monday.
His devastated parents Melissa and Mathew Mongoo appeared on 7 News, grieving the loss of their little boy whilst clinging to hope that their oldest son survives.
"I knew something was wrong when they didn't answer," Ms Mongoo told Channel 7.
Nulla's brother, 14-year-old Matt, is still fighting for life in hospital where he was reported to be in a serious condition on Wednesday evening.
Another boy who was present during the incident, a 12-year-old male friend of the pair also remains in hospital in critical condition.

Nulla's mother was emotional when speaking to Channel 7. From the moment her sons were transported to Perth's Children's Hospital she's been by their side.
"They gave their home to every boy out on the street, they were kind, they were caring, they loved every kid…" said Ms Mongoo.
"...I miss my baby…"
While Nulla's father remained quiet yet strong as he fought back tears whilst on camera.
"He was a mummy's boy, a bit cheeky," said Mr Mongoo.
The couple have spent every minute by Matt's side and therefore haven't been able to organise a funeral for Nulla or properly mourn.
"We haven't even had time to mourn properly, cry or anything," Mr Mongoo said.
The Mongoo family home was once filled with laughter and memories, now it will be demolished with the cause of the blaze remaining unknown.
"There is no home, we have no home now…" said Ms Mongoo.

A GoFundMe page has been established by Nadine Ryan, Ms Mongoo's daughter-in-law, the fundraiser created to help support the family during the tragic time in their lives.
Ms Ryan wrote, "...The youngest brother growing his wings has been hard for all, but especially unbearable for his mother…He was so brave and strong, he fought right to the very end..."
"...She was still mourning the loss of her second eldest boy who grew his wings in 2017 at 25 years young.
"With two sons with wings and one son fighting for his life, the heartache she is experiencing is unimaginable. No human, mother or parent wishes this upon anyone."
With Matt still in hospital in a critical condition, doctors and family are unsure of timeframes.
Donations will support practical items such as food, accommodation, fuel and clothing to help the family reestablish their lives.