His ancestors had come to Taiwan from Fujian and had been teachers in Taiwan for generations. One grandfather, Cao Tianxiang, founded and taught at a private school. His father, Cao Ciying, graduated from the normal division of the Office of the Governor-General's Japanese-language school (now the Taipei Municipal University of Education) and went on to teach at Shilin's Bazhilan Public School.
先祖自大陸福建來台後，世代皆以教書為業，祖父曹天相設私塾授業，父親曹賜瑩畢業於台灣總督府國語學校師範部（現台北市立師範學院），任士林八芝蘭公學校訓導。