Buenaventura was one of four siblings. His eldest brother, Cesar A. Buenaventura, was former Chairman and CEO of Pilipinas Shell, and is a partner at the investment advisory and merchant bank, Buenaventura, Echauz and Associates. His other brother, Jose, is a lawyer and is a senior partner at Romulo Mabanta, Buenaventura, Sayoc and Angeles Law Offices, one of the most prominent law firms in the country. His only sister, Elisa P. Buenaventura is a treasurer and board member of the Asian Social Institute in Manila.