Answer:
The main factor that helped Calvin overcome his disability is the support, love and dedication that his family has with him.
Step-by-step explanation:
Calvin's story, is a story of a lot of struggle and perseverance, as the question above says, since Calvin besides having a very slow physical and mental development, presents violent convulsions for long periods of time, which have already hurt him a lot. In addition, the strong remedies taken by him cause other problems to arise, harming Calvin as much as his disability.
But Calvin always overcomes his problems and manages to survive despite so many crises. This survival of Calvin is a result, mainly, of his family, since Calvin is very loved and cared for by his parents, who besides providing everything he needs, give him the greatest love in the world.