Central to this tragic tale is the inability of the elder brother, the narrator of this story, to allow his brother to be who he is. He is clearly driven to train and teach Doodle how to do physical activities that are mostly beyond him, and yet this compulsion is not borne out of a sense of love or compassion for his pitiful younger brother. Rather, the text makes clear that it is a sense of embarrassment and pride that leads the narrator to invest so much time with Doodle and try to "improve" him. Note that the text informs us that the narrator teaches Doodle to walk because he was "embarrassed" to have a five-year-old younger brother who can't walk. This leads to a moment of tragic realisation when Doodle displays his talent to their parents, and the narrator realises what motivated him to work with Doodle so hard:
They did not know that I did it for myself; that pride, whose slave I was, spoke to me louder than all their voices; and that Doodle walked only because I was ashamed of having a crippled brother.
Thus the narrator here himself identifies his biggest flaw: pride, who, as he says, had him in slavery. It is this same pride that leads us to the story's tragic conclusion. When the narrator and Doodle are forced to admit failure, note what the narrator says:
We never spoke (what are the words that can solder cracked pride?), but I knew he was watching me, watching for a sign of mercy.
Key to identify is the metaphor comparing the "cracked pride" of the narrator to an object that cannot be soldered together again or repaired. Doodle is described as desperately watching for a "sign of mercy," but this is something that, because of his slavery to pride, he is able to fulfil.
In a sense, then, Doodle meets his sad and tragic end precisely because of the flaw of his brother, who is unable to accept Doodle for who he is, with his limitations, and thus is driven by his pride to try and transform him into something that Doodle could never be.