What is doodle sacrificing for his brother?

In the story, Doodle sacrifices walking for his brother, who is embarrassed by his disability. Doodle tries to learn to walk so that he can be included in his brother's activities, but he is unable to do so. As a result, his brother is forced to carry him around, which becomes a burden. Eventually, the brother becomes so frustrated that he throws Doodle into a swamp and leaves him there.