My father is a mathematician. For most of my childhood he worked for Westinghouse, modelling nuclear reactors.
He was one of those lucky people who know early on what they want to do. When you talk to him about his childhood, there's a clear watershed at about age 12, when he "got interested in maths." He grew up in the small Welsh seacoast town of Pwllheli. As we retraced his walk to school on Google Street View, he said that it had been nice growing up in the country.