The blaze started in a granny flat this morning, prompting numerous Triple Zero calls from 7.41am.
The initial crew en route to the scene at Fairfield called for backup on seeing the volume of smoke as they approached.
The fire had extended to a two-storey main residence when firefighters arrived.
Ultimately, nine trucks were dispatched to the scene, with 36 firefighters deployed in total.
They were able to bring the fire in both buildings under control and are now conducting final extinguishing.
Three adults and two children, including the baby, were able to flee the fire.
The two children were treated by paramedics.
9News understands the baby, who suffered smoke inhalation, was taken to hospital with non-life threatening injuries.
Fire investigators will examine the scene later in the day.