He was born on 6 September 1939, the son of Néstor Rolando Fuentes Venegas and Josefina Venegas González. He married Sonia Hélia Rojas Soto in 1974. He studied law at the University of Chile and was admitted to the bar in 1963. He practiced as a lawyer in San Carlos.
He began his political career by joining the Christian Democratic Party, where he served as secretary general of the Command for San Carlos and Itata during the 1964 presidential election. In 1965, he was elected Deputy for his constituency, a position he held through three consecutive terms.
During the 1965–69 term, he was a member of the Permanent Commissions on National Defense, Economy and Commerce, Constitution, Legislation and Justice, Housing and Urban Development, as well as the Budget Joint Commission and several special investigative commissions.
In the 1969–73 term, he was elected Second Vice President of the Chamber (from 22 June 1971 until 15 May 1973) and served on numerous standing and special committees including Constitution, Bank Credit Concessions, Constitutional Accusation, Constitutional Reform Application, Banking Transactions, and Investigations into Violence in the Investigation Service.
In the 1973–77 term, before the early termination of Congress, he was a member of the Permanent Commission on Constitution, Legislation and Justice. He also sponsored motions that became law, such as Law No. 17,530 (25 October 1971), on the transfer of public housing occupants in San Carlos, and Law No. 17,580 (29 December 1971), regarding payments for mayors and former mayors.
After the forced interruption of his mandate due to the military coup on 11 September 1973 and the official dissolution of Congress on 21 September, he continued his legal practice and remains a respected figure in local politics.