I want to locate a person but I have little information

I recently found out that my grandfather isn't my dad's biological father, and I was told a few things about him. I tried searching online myself, but I couldn't find anything (which makes sense since what I know dates back to the 1970s), so I thought I'd ask here. I know his name is Gustavo Zúñiga. He must have been born in the 1940s. He had a wife and children, if I'm not mistaken, a girl and a boy born between the 1960s and early 1970s, and by 1973 he was working in the Valparaíso treasury. In 1972, he was unfaithful to his wife and had a son (my father) with a young woman from Valparaíso. He didn't take responsibility for the child, but he did meet his son when he was very young. If anyone recognizes this person, or has any ideas that could help me, I would be very grateful. Thanks in advance :)