Joined a Wilderlands campaign setting game in 1979 that had been going for a while. The game was run by some folks that my mother knew. I was 8 years old, and had just finished my first reading of Lord of the Ring (minus that one chapter in book one that was basically people sitting in chairs and talking...).
My mother would have been 25 at the time, so that's probably roughly the age group. Some of them were part of a local juice co-op (Genesis Juice, Eugene, OR); otherwise I didn't know any of the "adults".
My best friend (age 9) also joined the group at the same time. I'll never forget the first time he rolled a d4 for his first-level Magic User hit points: it landed on its tip. Neither he or I had ever seen the die rolled, so we didn't know how to read it. Needless to say, the guy that was helping us make our characters immediately jumped up to go get the rest of the group from the other room where they were playing so they could witness. I've never seen a d4 land like that in 30 years since.