Further inspection of the home in Kambah after the fire was put out has revealed more damage.
The fire in the bedroom also got in to the roof space and the damage bill could be hundreds of thousands of dollars.
Firefighters say it's important to have a plan in place for children in the event of a fire.
In this case, a 12 year old boy was left in charge of his younger siblings and did everything right, evacuating the house immediately and notifying neighbours.
Firefighters say it could have been much worse.