 Kaino was born on 6 April 1983 at Lyndon B. Johnson Medical Center in Faga'alu, located in the U.S. territory of American Samoa as the third of six children.In 1987 at the age of 4, he and his family relocated from their home village of Leone, Tutuila, to Papakura, Auckland.After settling in Papakura, he played junior rugby league for the Papakura Sea Eagles before switching to rugby union in secondary school at Papakura High School and Saint Kentigern College where he was offered a rugby scholarship.