The son of Isaac Driver and Adi Asenaca Mairara, Siwatibau was born on 4 November 1940 in Tukavesi Village in Buca Bay, Cakaudrove Province, but grew up in Buca, the village of his mother, who was of chiefly rank.
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While at Auckland University, he had met his future wife, Suliana Kaloumaira, a native of Moturiki Island.
A native of Moturiki Island in the Lomaiviti archipelago, Siwatibau was married to the late academic leader and former Vice-Chancellor of the University of the South Pacific, Savenaca Siwatibau, from 1966 till his death in 2003.