Mick Fanning has paid a touching tribute to his brother who died overnight saying: "like all my big brothers, Peter will always be a hero to me".
Reports of his brother's death emerged during his quest for his fourth world title at the Pipe Masters event in Hawaii.
Fanning vowed to keep competing, saying he knew that's what his brother would have wanted.
He also said his brother loved seeing him compete, signing off with the heartfelt sentiment: "Tell the special people in your life you love them and give them a hug".
The Gold Coast Bulletin reports that a close family friend has confirmed the death, saying Peter Fanning was staying at Fanning’s southern Gold Coast home following his recent divorce. The paper reports that Peter, 43, had three children.
Fanning lost another brother, Sean, in 1998. He died in a car accident.
This has been a year of incredible highs and lows for the 34-year-old three-time world champ. In July, he astounded the world with his bravery when he punched a shark which attacked him during the J-Bay Open surfing event at Jeffreys Bay on South Africa's east coast.
That event was subsequently called off and Fanning missed out on crucial championship points which may have secured this year's World Surf League (WSL) crown long before this week's final event in Hawaii.
But Fanning now remains locked in a three-way title battle as the event enters its final rounds. Fanning is believed to have competed after receiving the news of his brother's death, winning his round three heat in powerful three metre waves.
Fanning has since advanced to the quarter finals of the event which is taking place live on Thursday morning (AEDT) after winning his round four heat.
On the final wave of the heat, which scored an impressive 9.30, Fanning held his hands aloft triumphantly after emerging from a barrel. He then appeared to turn his head to the heavens in scenes reminiscent of Australian cricketers saluting fallen cricketer Phillip Hughes -- and jockey Damien Oliver glancing skywards after winning the 2002 Melbourne Cup the same week his elder brother Jason had died.
The contest continues on Friday morning AEDT. Fanning's quarter final is against Kelly Slater, who's probably the greatest surfer of all time and who has won this event seven times. Fanning has never won it. Not for the first time this year, the Aussie has quite the surf battle ahead of him.
The good news is that one of the America commentators seems to think he has a great chance.
"The guy’s got a mean flow going right now," the commentator said of Fanning. We'll assume that's a positive comment.