Enda O’Donoghue, 23, from Ardrahan in Co Galway, died when he was struck by a car.
It is the second tragedy to hit the family in recent years, as his brother Aidan drowned in a river in Ennis, Co Clare in 2005.
Enda O’Donoghue, a carpenter, moved to Ingham near Townsville in Queensland five weeks ago to join another brother who was working in construction.
Ardrahan parish priest Fr Joseph Roche said the community was shocked at the latest tragedy to befall the O’Donoghues. A family friend said Enda’s parents, Bernie and Marie, and four siblings were devastated.
Police said Mr O’Donoghue was attempting to cross a road in Ingham on Friday night when he was struck by a car.
He was rushed to Ingham Hospital in a critical condition before being flown to Townsville Hospital, where he died on Saturday morning.
The driver of the car was not injured and an investigation is continuing.
His older brother, Aidan, was 27 when he disappeared in the early hours of Jan 2005 after attending a disco.
His body was found in the River Fergus a week later.
A post mortem examination found he had drowned and an open inquest verdict was recorded.
The O’Donoghue family argued there were reasons to believe Aidan might have been assaulted and robbed shortly before his death.
Meanwhile, the Health and Safety Authority is to investigate the death of a man in a farming accident in Kerry on Saturday.
The man, aged 59, died after becoming trapped under a tractor and trailer he had been repairing in Listry, Beaufort. He was taken to Kerry General Hospital but was pronounced dead there a short time later.
Two people were also killed in road crashes in counties Louth and Cavan at the weekend. On Saturday a man in his 20s was killed in a single-vehicle crash in Co Cavan when a car left the road at Drumcor shortly after 6.30am. A male passenger in his 20s received non life-threatening injuries.
Gardaí have appealed for information about a fatal accident in Co Louth, where a man aged 27 was struck by a minibus as he walked from Carlingford towards the Dundalk road at around 2.45am.
Several passengers were on the bus but were not injured and gardaí have asked any passengers who left the scene to come forward.
Meanwhile, a body recovered from the Shannon Estuary yesterday is believed to be that of a Limerick man missing for five weeks.
Volunteer teams had been searching for father-of-one Kevin Mulqueen, 40.