Pa Maretu was adopted by Obura (born ca. 1836), who was the son of Maretu I (1802-80), one of the first Christian converts (in 1823) on Rarotonga, the main island in the Cook Islands in the South Pacific. Obura was a missionary and the husband of High Chief Pa Te Upoko Ariki Tini. They had no children and so adopted Maretu, who was the son of a Rarotongan woman and a French man.
Pa Maretu succeeded his mother to the title of high chief of Takitimu in the mid-1890s. Possibly because of his mixed ancestry, he was the only native high chief respected by both the Rarotongans and the New Zealand colonial administrator, W.E. Gudgeon. In 1902 he was appointed an associate judge and advisor on native customs to the Rarotongan Land Titles Court.
He died sometime before 1908.