The short, shattered life of 4yo Willow Dunn and the Kiwi father accused of killing her

Willow Dunn was found dead in her Brisbane home. Photo / Facebook

Police investigating the horrific death of a 4-year-old girl in Brisbane are trying to build a picture of the youngster's life and won't rule out further charges.

Willow Dunn was found dead in her cot on Monday after allegedly suffering prolonged mistreatment. Her body had lain there for days.

New Zealander Mark James Dunn, 43, the child's father, has been charged with her murder.

Willow Dunn was found dead in her Brisbane home. Photo / Facebook

Willow lived in the Cannon Hill home with her father, her stepmother, Shannon White, White's adult daughter and a young boy, news.com.au reports.

The girl, who had Down syndrome, was allegedly left to starve in a filthy bed in a bedroom. Her body had been attacked by vermin.

A post-mortem examination this week revealed Willow was "experiencing serious malnourishment, along with many other health concerns that supported sustained mistreatment".

Mark Dunn, father of the four-year-old girl who died in the family's Cannon Hill home, has been charged with murder. Photo / Facebook

A friend of the family told the Sunday Mail White – who has not been charged – seemed like a doting mother to her biological children.

The newspaper viewed messages sent by White to friends describing her parenting of her own children.

"He's like four inches from my bed, I'm a helicopter mum lol," White said in one message last year, The Sunday Mail reported.

Last week, the Courier-Mail alleged White told police officers at the scene that she wanted "nothing to do" with the little girl.

Neighbours of the family told the newspaper they never knew Willow existed.

"They've been there for that long and we didn't know a little girl lived there," one neighbour said. "I can't believe it."

Willow's biological mother, Naomi Dunn, died suddenly just days after giving birth due to complications.

White was the woman's "best friend" of 20 years, the Australian reported, and was bridesmaid at her wedding in 2014.

She and Willow's father began dating after the sudden death, but the newspaper reports White didn't play a role in parenting the girl.

Shannon White, the stepmother of Willow Dunn, has not been charged. Photo / Supplied

Queensland's Child Safety Minister Di Farmer has ordered an independent investigation into Willow's death, as well as a separate horrifying case involving the neglect of two disabled teenage brothers who were found living in a locked bedroom in a squalid home in Brisbane.

The boys' father died in the front yard from a suspected heart attack and when police arrived, they heard noises coming from a room and found the boys, naked and filthy, in a distressed state.

Willow Dunn's mother, Naomi Dunn, died just days after giving birth. Photo / Supplied

They were rushed to hospital where they remain in a stable condition.

Cheryl Vardon, the head of the Family and Children Commission, will lead the probe.

On Friday, police insisted their investigation into Willow's death was ongoing and wouldn't rule out further charges.