I grew up hearing "harmony" sitting in church between my mom and dad.
They both sang parts and knew how to harmonize so I heard that from the time I was born with my mom singing in my ear and around the house, at church, etc.
I remember distinctly when she taught me the alto part because I and my two sisters had been asked to sing in church. I was about 6 at the time. After that *harmonizing *was just a natural part of singing.
I was always involved with music - took piano for 8 years - played in church and was always involved in trios, choir, and so on.