Somewhere around age 2, simply messing around with the NES that my mom owned.
I think I wasn't allowed to touch it, but seeing the characters on screen made me want to mess around with it. By age 3 I was playing Mario, Zelda, and Mega Man games, and knew at least how to control, and even progress through them, though I wouldn't be beating games for a little longer.
By 4, my mom upgraded to the SNES that had been out for years already.
Age 7, I got a PSone as the first console that belong to me.