Julio Mario Santo Domingo was born on 16 October 1923 in Panama City, Panama, to Julio Mario Santo Domingo Santo Domingo and Beatriz Pumarejo de Vengoechea, the youngest of their four children; his older siblings were Beatriz Alicia, Cecilia, and Luis Felipe. His Father was a banker, described as austere and disciplined, who made a fortune buying companies weakened during the Great Depression; his mother, from a rich and influential family, was first cousin of Alfonso López Pumarejo who was twice President of Colombia. He grew up in Barranquilla and later attended the exclusive Gimnasio Moderno in Bogotá, D.C., ultimately culminating his secondary studies at the Phillips Academy in Andover, Massachusetts; he later attended University of Virginia before transferring to Georgetown University, but did not finish his degree.
He first married to Edyala Braga Brandão do Monte, a Brazilian socialite, daughter of Brazilian ambassador in Paris and former wife of Brazilian President Getúlio Vargas' brother. Together they had one son, Julio Mario Santo Domingo Braga (1958–2009), but the marriage did not last long and they divorced shortly after.
He remarried on 15 February 1975 to Colombian socialite Beatrice Dávila Rocha, and together they had two sons, Alejandro Santo Domingo Dávila (b. 1977) who has continued on in the family Business and Andrés Santo Domingo Dávila (b. 1978) the co-founder and President of Kemado Records, whose 2008 wedding to the socialite Lauren Davis (then founder of the online fashion retailer Moda Operandi).
The Group has a majority stake in Bavaria Brewery and Valores Bavaria (a holding company for his non-beer interests). In 2005, Bavaria Brewery merged with South African company SABMiller. In this merging, the group acquired 15.1% of SAB Miller, becoming the second-largest shareholder of the second-largest beer company in the world (behind Anheuser-Busch InBev).