My dad use to let me sit next to him and steer. That started when I was 3yrs. And then he started teaching me as soon as my feet could reach the pedals, I'd say aroung 6 or 7. Oh, I must add, not in public places!
Since I was in a constant state of being "grounded", I did not receive my license until I was 17. :sad2: At the time it felt like the end of the world that I had to wait that extra year.