My oldest sister and I have talked about this many times. I never had a "rebellious phase", but she did. With my parents permission, she taught me all about alcohol and weed when I was around 12/13. I believe her openness kept me from doing those things. She is eight years older than me, and she always told me growing up, "Look at my mistakes, and don't do them. I learned the hard way... You don't have to." I credit my sister for protecting from things I didn't need to get involved with. She has a one year old girl now, and she says she will always be very open with her daughter as she grows up. I plan to do the same. We both saw what it did for my life.