Born in Tangerang into the ‘Cabang Atas’ aristocracy, Oey was the son of Oey Jan Long Sia and a grandson of Oey Eng Sioe, Kapitein-titulair der Chinezen. As a descendant of a Chinese officer, he bore the title ‘Sia’ from birth. Oey was married to Nie Kim Nio, daughter of Nie Boen Tjeng, Kapitein der Chinezen in Batavia and a descendant of Kapitein Nie Hoe Kong, who was in office during the Chinese Massacre of Batavia in 1740.