Born in Batavia into one of the colony's richest families, Oey was the son of Oey Makouw Sia, and was through his father a grandson of Oey Thai Lo, der Chinezen, and a nephew of the murderous playboy Oey Tamba Sia. As a descendant of a Chinese officer, he bore the title ‘Sia’ from birth. He married Ong Dortjie Nio, who came from one of the oldest families of the ‘Cabang Atas’ aristocracy. Oey's father-in-law was the landlord Ong Boen Seng, while his mother-in-law, Nie Koen Nio, was the daughter of Nie Boen Tjeng, Kapitein der Chinezen in Batavia, and a descendant of Kapitein Nie Hoe Kong, who was in office at the time of the Chinese Massacre of Batavia in 1740.