It is understood the family lives in Opononi. Robbie's father and a brother were at the farm in Mataraua when the accident occurred. The rest of the family is overseas visiting relatives.
The tragedy is likely to renew scrutiny of quad bike safety as well as access to emergency medical help in the Far North.
WorkSafe is urging farmers to take special care on quad bikes after two deaths this week. The other was on Tuesday on a Wairarapa farm.
National programmes manager Francois Barton said the two tragedies were a reminder to the farming community that quad bikes, while a useful tool, had to be used safely.
"Five people died on quad bikes in 2014 and many were seriously harmed. Using a quad safely comes down to the attitude of the user, their safety practices, making safe choices and using the bike responsibly."
WorkSafe launched a Safer Farms programme in February partly in response to concerns about quad bike safety.
Recent serious quad bike accidents in Northland include the death of a 42-year-old man at Ruawai in October after his quad bike rolled and trapped him in a flooded drain. Earlier that month a 14-year-old girl was seriously injured when a quad bike rolled and pinned her down in a swamp near Ahipara, while in August a 31-year-old Whangarei man suffered serious injuries in a recreational quad bike accident in sand dunes at Pouto.
In 2010, three Northlanders died in farm quad bike accidents in just eight weeks. That spate of fatalities sparked a coroner's investigation aiming to find ways of preventing future accidents.
WorkSafe's advice for managing quad bike risks:
•Riders must be trained or experienced enough to do the job.
•Choose the right vehicle for the job. Don't carry passengers and tow too much.
•Always wear a helmet.
•Don't let kids ride adult-sized quad bikes.
•Keep bikes in a safe condition.
•Take care on slopes and rough terrain. Don't exceed the bike's capabilities.
•Don't do tasks that interfere with safe riding. Keep both hands on the bike and eyes on the ground in front.