I'm the youngest of three boys. We were all D1 athletes. I'm the slowest by a pretty substantial margin.

However, I matured faster than my brothers and, having been able to observe them, picked up proper techniques and approaches to training earlier than they did. As a result, I broke many of their age-group records. Once I stopped growing, however, it came down to who had the most physical / mental talent (not me).

The other thing to mention is access to training. When I was in middle school, I was able to train with the high school team because my middle brother included me. I even got to go on the winter training trip to Florida with the high school team. That access to training with older kids who were bigger, faster and more mature accelerated my development both physically and mentally.