What quality does the brother in "The Scarlet Ibis" show?
Very perceptive question. The narrator, known as "brother" to Doodle, seems to spend most of the tale wanting to shape his brother into something that he actually isn't. From the start we can see that his teaching of Doodle to walk isn't actually out of love for him, but rather because he feels ashamed that his younger brother cannot walk, and wants to meet the goal he has set for him to learn how to walk. Note how the narrator tells us this information:
When Doodle was five years old, I was embarrassed at having a brother of that age that couldn't walk, so I set out to teach him.
Interestingly, when Doodle and the narrator reveal Doodle's new skill to their parents, they misinterpret the narrator's tears at the sight of Doodle walking:
They did not know that I did it for myself; that pride, whose slave I was, spoke to me louder than all their voices; an that Doodle walked only because I was ashamed of having a crippled brother.
Thus when we think of the narrator and his character, what strikes us most is his inability to accept his brother's physical condition. He is responsible in part for Doodle's death at the end of the story because he pushed Doodle to the limits of his strength and then abandoned him to die. His desire to help Doodle has far more to do with his own pride rather than love for his brother.
It is true that Doodle's brother showed self-interest in advancing his skills, and that he wanted a brother he could be proud of. The 'quality' I would say that he showed was perseverance - however this is difficult to detach from that original self-interest. It was his brother's refusal to give up that resulted in Doodle being able to accomplish so more than any older ever thought he could - or maybe should. (For we must remember that adults may have been putting the small crippled child's needs first, in not pushing him to achieve greater physical independence and more developed skills - perhaps it was the adults who cared most for Doodle.) It would have been interesting to hear the crippled boy's own opinion as a grown up - sadly, due to his brother's obstinacy, we never get to hear the benefit of Doodle's hindsight. His brother would probably suffer from feelings of responsibility and guilt for a very long time, but we must also remember that he was only a child too.