The Weekend Herald has uncovered these photos of Williams' early days as a member of the Marist Saints league club and Junior Kiwis representative sides.
However, Williams was more than just a gifted league player. At the Roskill South Athletics club he was a promising sprinter and high jumper. He still holds the club high jump record for 10-year-olds of 1.43m.
"He was an exceptional high jumper," recalled Anne Lipscombe, wife of Ross, who was a long-serving club president.
Mrs Lipscombe said Williams was a "little bit temperamental" as a child. He had been tipped to have a promising future in athletics but gave up the sport when he was about 12.
Williams' record mark has since been tied by Ben Lamb, a member of the All Blacks Sevens team. Kiwis winger Antonio Winterstein is also among the talented sportspeople to have passed through the club.
"Athletics is a foundation sport for things like running and jumping," current club president Peter Wyatt said.
"Most good rugby and league players have come through athletics at some point."
Warriors and Kiwis back Jerome Ropati was a teammate of Williams in the champion 2001 Marist colts team, which also included his older brother John Arthur and was coached by his father John.
Williams' twin sisters Niall and Denise were also talented athletes, with Niall becoming a representative touch player.
Williams' grandfather Bill Woolsey, who died in 2004, was a legendary figure on the Auckland league scene and noted boxer who was known for his toughness.
Williams, who has a Rugby World Cup and Super Rugby title to his credit from a five-year spell in union, returns to his league roots tonight when his Sydney Roosters club takes on the Warriors at Eden Park.
The match has been hyped as the Warriors v Sonny Bill, with Williams' image even used in advertising for Warriors club-membership offers.
Despite the club being in the midst of a record worst eight-match losing streak, Warriors officials are hoping for a crowd of 30,000.
