A joint inquest into the deaths of four unrelated children who were involved with Victoria's child protection system is underway.
The body of one child, two-and-a-half years old, was found in a roof cavity, counsel assisting Teresa Porritt told the Victorian Coroners Court on Friday.
Autopsy results showed internal blood loss associated with blunt force trauma.
Three notifications had been made to Child Protection regarding her family during the child's life.
An investigation then found concerns about exposure to family violence, physical discipline and drug use.
The child's mother's new partner was also found to have an extensive criminal history that included family violence.
Another child, in her teens, was killed alongside her mother and the woman's partner in a fire deliberately lit by her ex-partner, who was convicted and jailed.
Multiple reports were made to Child Protection in relation to the girl and her siblings before her death.
They involved concerns surrounding exposure to parental drug use, mental health issues, family violence, neglect, environmental concerns, homelessness and sexual abuse.
Meanwhile, a six-month old boy died after Child Protection was advised his mother was homeless and used drugs including ice and GHB.
Medical examinations found the baby's death was likely caused by shaking, while there was also bruising to his face.
A man, with whom the boy's mother had recently started a relationship, was convicted and jailed.
The last child died in 2017 after she was stabbed once in the neck by her mother when she was 10 months old.
A total of five reports had been made to Child Protection in between 2013 and May 2017 regarding her mother's unstable mental health.
The inquest, heard before Judge John Cain, will examine the four deaths in two separate fortnight-long hearings, starting from January 31 and August 1.