My wife (RIP) our girlfriend (DD1 and DD2's Mom) and I started eating less meats around 16-17 ('76-'77). We all had jobs so switching from our parents meat eating ways was easy for us. By the time we were 20 we were vegetarian along with a little fish here and there. Adding vegan meals was a natural fit for us.
My girls have always eaten vegetarian/vegan diets. DD1 tried red meat once, was totally grossed out, spat it out and said never again. DD2 has never had an interest in trying any meat, thinks it's gross. Their spouses are also vegetarians/vegans.