And as if that wasn’t enough of a coincidence, they all fly from the same club!
“We’re a family affair and we’ve established a fantastic team spirit over the years,” said Uys Jonker.
“We give each other nice support and we’re having fun.”
In open class another set of brothers, Laurens and Oscar Goudriaan, say they’ve cultivated a successful team dynamic over a number of competitions.
“Part of being a successful team is you have to have a strong understanding, even between the pilots and crew, so we put a lot of effort into selecting our crews as well,” said Oscar Goudriaan.
The brothers have been flying together for more than 30 years and say there’s no family politics involved in flying together.
“If he wants to go his own direction that’s fine, but generally we discuss things and from there we make a decision,” Oscar said.
“Sometimes we go his way, sometimes we go mine, and generally it works well.
“We know each other’s flying styles but I don’t really think it’s a competitive advantage.”
Possibly the youngest pilot in the championship, 21-year-old Marcus Nouwens, is flying with his father, Pieter.
Marcus made the decision to fly at the World Championships, rather than the junior worlds, so he could fly with his father.
It is the first world competition for both of them, and Marcus said the family atmosphere works in the team’s favour.
“We’re very chilled,” he said.
“We take it seriously, but not so seriously. We’re not here to joke around, but we are here to enjoy ourselves.”
As for flying together, the 18m competitor said he could be much more open with his father.
“And he can definitely be very open towards you!”
The six pilots all fly out of Potchefstroom, about 120km from Johannesburg; a club founded after Attie and Uys Jonker attended University in the town, and their father had moved there to be closer to the boys.
“We decided it was time to have a club,” says Uys Jonker.
“So myself, Attie, Oscar, my Dad and one of our other friends, we were five guys, all instructors, we had a meeting and we started the club,” he said.
“Because we started cross country flying and intensively preparing for competition we attracted other high-level members like the Nouwens’s who live 350km away.”
It’s a great training ground for people like Marcus Nouwens, who is aiming to be South African national champion by the time he’s 30. He said he aspires to follow in the footsteps of the Jonker brothers.
“I’m extremely competitive,” he said.
“When I go flying I don’t just launch and hang around the airfield. I always want someone to fly with because I want to have a race with them. It’s my competitive side that keeps me going."
With an estimated 30 competitive pilots in South Africa, they’re a rare breed.
“It’s a once off,” Ms Clifford said of the team full of relatives.
“I don’t think there’s ever been such a family affair in a worlds,” she said.
“The fact they’re also all flying Jonker sailplanes is a fantastic success story. It’s just 10 years since they first test-flew the first Jonker sailplane, it’s incredible.
“It gives you a warm, fuzzy feeling about what they have achieved.”