My parents let me have my first glass or two of wine with dinner when I was 13. I remember distinctly - we were on vacation on a cruise so it was a special occasion. I didn't think too much about it one way or another at the time. It just made me tired.
I started drinking alcoholically at around 14-15. I didn't drink all the time, but when I did I couldn't stop. And so set the pattern for the rest of my drinking life.