Jamie, Ewan and Lachlan Maclean have covered more than 14,000 kilometres from Peru to Australia's far northern shores where they will become the first team to finish the full crossing.
They are due to land in Cairns on Saturday after strong winds nixed plans for a Friday arrival.
Storms, sickness, injuries and being thrown overboard are all obstacles the brothers have endured in a quest that has raised more than $1.52 million (Stg730,000).
The money will fund projects that provide clean water for people living in Madagascar through their own charity - the Maclean Foundation.
The brothers aim to provide clean water for 40,000 people, declaring it the "most basic of needs" and too often taken for granted.
Supporters of the trio include movie stars Ewan McGregor and Mark Wahlberg and Flea from the band Red Hot Chili Peppers.
The brothers grew up in the northern tip of Scotland in the village of Nedd, where they thrived in the brutal conditions.
"The weather's just been against them constantly," Greg Hollerin, a close family friend who manages their campaign, told AAP on Friday.
"They've kind of been outdoorsy and they've always wanted a challenge from their kind of unusual upbringing."
They have raised hundreds of thousands of dollars from sponsorships with renowned whisky distilleries such as Rare Whisky 101 and Talisker, paying tribute to their father's background as a whisky expert.
Mr Hollerin said youngest brother Lachlan was inspired and humbled after a volunteering trip to Madagascar, where he witnessed how crucial clean water was to people's survival.
"They feel very lucky about and privileged about the life they have had and when Lachlan went out there to Madagascar, it kind of changed his life ... and now they've dedicated their lives to this cause."
After setting off from Peru on April 12 and 139 days at sea, the trio will be welcomed by more than 50 friends and family from the UK - including their mother Sheila - when they row into Cairns on Saturday.
Middle child Jamie, while keen to see friends and family, is looking forward to one particular land-based delicacy.
"All I want is a pizza," he said.
Ewan has described the journey as the hardest thing he has ever done and one he couldn't have contemplated without his siblings.
"We've shed tears of joy and laughed till our cheeks hurt," he said.
"And at times we've cried with sadness and with fear, but our spirits have been lifted, time and time again, by the support of so many rallying behind us."
Their craft is named Rose Emily, after a sister their parents lost during pregnancy.
The trio previously broke world records when they rowed from La Gomera in the Canary Islands to Antigua in 35 days.
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