Father Ken Franks, 50, tells how Owen decided to hide during a fishing trip in the Marlborough Sounds on his commercial trawler, sparking a minor emergency when the family thought he had fallen overboard. Owen emerged from his hiding place as they were about to turn the boat around.
As props, the Franks brothers will provide the platform upon which New Zealand's World Cup aspirations rest.
At 23, Owen is a propping prodigy - already touted as the world's best tighthead in a position where most players only reach their potential in their late 20s.
Ben, a 27-year-old utility who can cover both sides of the scrum, is more likely to join the action from the bench.
Ken Franks took an interest in their development from an early age, schooling them on agility, sprint work and weight training.
They weren't naturally big at school, weighing around 85kg when they were first selected for the Christchurch Boys' High School First XV in Year 12. But the daily regime of eat-train-eat-train eventually saw them pack on the pounds.
They now weigh in around the 117kg mark - just don't call them fatties.
Back in 1999, the brothers, with mother Julie and sister Kate, were caught in a house fire in Lyttelton. Quick thinking by Ben saved them.
After waking the family, he went back into their home to pull out Owen, who was sound asleep. And Owen says they still rely on each other on the field. "It's like playing with your best mate."
Ben and Owen's parents separated when the boys were still young, and Ben says their mother's contribution to their development is sometimes overlooked. "She kept us fed as youngsters, which was quite an effort," he laughs.
The two boys would get through eight sandwiches for lunch, or pile through eight eggs and 10 Weetbix for breakfast.
"She provided that balance. It would have been a bit too much having two parents who were rugby mad."
The boys often take time to remember their grandfather on Father's Day.
Ken senior died suddenly at 62, and there is a lingering sadness he wasn't around to see the brothers become All Blacks.
Owen says: "He was cool. He was really good with his hands, he made us cricket bats, but he was also a disciplinarian. I guess he instilled some of those values in us."
Both men have long-term partners. Ben's partner of seven years, Jenna Underwood, recently gave birth to their first child, 4-month-old Annabel.
And Owen has been dating Christchurch travel agent Emma Vieceli. He says the players will have one day off a week to spend with partners during the tournament.
