Born in Chiayi City, Siew graduated from the Department of Diplomacy at National Chengchi University in 1961, and received a master's degree from the Graduate Institute of International Law and Diplomacy at National Chengchi University in 1965.
He worked at the ROC's Consulate General in Kuala Lumpur from 1966 to 1972, until the Republic of China left the United Nations (see China and the United Nations). He was named to the Central Committee of the Kuomintang in 1988. He was appointed was Minister of Economic Affairs from 1990 to 1993, and elected a member of the Legislative Yuan from 1996 to 1997. He was the vice-presidential candidate in 2000, paired up with Lien Chan (see ROC Presidential Election 2000).
Siew is married to Susan Chu (朱俶賢 Zhū Xiánshú) with three daughters: Ru-ting (蕭如婷), Jia-feng (蕭如芬), and Jhih-you (蕭至佑 Zhìyòu).
See also: Politics of Taiwan