The Tuohys didn’t tell the story; the moviemakers did. By your logic, the film company wasn’t obligated to share the proceeds of the movie. If the Tuohys were entitled to share the movie’s profits because it was about them, then so was Oher entitled to share.
Oher was 23 by the time the movie came out, and more than legal age. Wouldn't the film company be obligated to make sure he legally got a part of the film proceeds?