Parts of the attack were captured by a GoPro inside the house, as Liam torched the side of a television as a man lay sleeping metres away.
The two brothers fled as the house became engulfed with flames without attempting to rouse the sleeping occupants.
“Less than three minutes later the house was on fire,” Judge Pillay said.
Three residents were able to escape without injury after waking up to a home full of smoke.
Despite efforts by firefighters, the blaze destroyed the home, causing an estimated A$250,000 in damage.
Later the same day, Liam was confronted by one of the occupants on social media over the fire, threatening physical violence if she didn’t keep quiet.
Liam pleaded guilty to arson, threat to inflict serious injury and reckless conduct endangering persons and will be eligible for parole after two years and six months.
The court was told he had previously been jailed for arson and was on parole when the offending occurred.
Luke, who stood by as the incident unfolded, pleaded guilty to reckless conduct endangering persons and will be eligible for release after serving 12 months of his sentence.