Andy Spencer is a male Tau'ri, and the son of Joe Spencer and Charlene Spencer.
In the far, distant past, at least one Ancient became an ancestor in Spencer's family line, passing down the Ancient Technology Activation gene to him. (SGA: "Citizen Joe")
When Andy was growing up his father told him stories about an elite team called SG-1. Andy loved the stories when he was young. (SG1: "Citizen Joe")