William Dunlop died following injuries sustained during a practice session at the Skerries 100 Road Races on Saturday. His father Robert Dunlop was killed while racing North West 200 in 2008, uncle Joey Dunlop was killed while racing in Estonia in 2000.
Loughshinny Motorcycle Supporters Club confirmed the news in a statement.
The Loughshinny Motorcycle Supporters Club, organisers of the Skerries 100, extended its heartfelt sympathy to the Dunlop family circle and took the decision yesterday to continue with the event "following discussion with the family, their sponsors and fellow riders". It's a family very much in our thoughts right now.
William was a hero to many in these parts and the community will be devastated at this news.
Dunlop recently revealed he was expecting a second child with his partner Janine.
He returned for the Isle of Man TT last month, but William chose to return home to be with his pregnant partner Janine, who was concerned about their unborn baby following a worrying 20-week scan.
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The Dunlop family also knows tragedy all too well. William's younger brother Joey Dunlop is third on the all-time winners list at the Isle of Man, behind 23-time victor John McGuinness and the legendary Joey Dunlop.
The Ballymoney rider is thought to have been riding his Temple Gold Club-run Yamaha YZF-R1 machine when he crashed at the Sam's Tunnel section of the 2.9-mile circuit.
Tributes have poured in for Dunlop, who secured 108 Irish National Road Race wins during a distinguished career.
Motorcycle legend William Dunlop has been killed after a tragic accident in in Co Dublin.
Like other members of his family, William Dunlop was a regular competitor in road races such as the North West 200, Ulster Grand Prix and, of course, the Isle of Man TT.
"Motorcycling was his life and he will forever be remembered for his many achievements, both in Ballymoney and across the world", she Tweeted.