Similar to playfair's son, my boy was also a tall skinny kid with a July birthday (always the youngest on a team of bigger stronger players). Son never made those circumstances an excuse, but instead treated them as a challenge. Although he never did become the strongest player physically, I think he did become one of the stronger players in other ways - mentally he is very tough.
That "training" served him well in High School. After making varsity as a Sophomore and pitching well that year he hurt his pitching elbow that Summer and wasn't really healthy again until his Senior season. Continued hard work and perseverance allowed him to overcome missing his critical Junior season - lead his team to a section championship his Senior year and earn the opportunity to pitch for a D1 program. Taking this different path has again made him mentally even tougher.
The challenges and obstacles haven't gone away, in fact they are bigger than ever - but he's fighting very hard to make the most of his opportunity. He still far from being physically strong (he's 6'2" and only 167 llbs), but (warning: parent bias coming) he's one of the "strongest" people I know.