It’s thought the attack could have been a case of mistaken identity, with the family not known to police.
Police are searching for four people who allegedly forced their way into the family’s home on Lucas Road, Burwood, masked and armed with a crowbar just after 2am.
All four members of the family – a mother, father and their adult son and daughter – were allegedly assaulted by the group, who stole car keys and a phone.
The group allegedly fled on foot, leaving the family’s car in the driveway.
Paramedics treated the family before they were taken to hospital.
The father suffered a serious head injury, but all are in stable conditions.
Forensics arrived on scene early this morning and have established a crime scene.
Neighbours have told Today they were shocked the incident had occurred in their neighbourhood.
“It’s unbelievable,” one woman said.
“After Australia Day, we all know it’s a safe country.”