"The Scarlet Ibis" is possibly one of the saddest short stories ever written. It tells the story of Doodle, the younger brother of the first-person narrator, who is born with severe handicaps. Although he is not expected to live, he does, eventually learning to follow his brother, the narrator, around.
However, the narrator is disappointed with having a brother like Doodle. In his mind, a brother is somebody you can do things with, a friend who shares your interests. Early in the story, the writer, James Hurst, establishes this idea:
I wanted more than anything else someone to race to Horsehead Landing, someone to box with, and someone to perch with in the top fork of the great pine behind the barn, where across the fields and swamps you could see the sea. I wanted a brother. But Mama, crying, told me that even if William Armstrong lived, he would never do these things with me.
As Doodle grows older, he gains more physical ability, and the narrator takes it upon himself to train and develop Doodle into a kid who can fit in with regular kids when he starts school:
Once I had succeeded in teaching Doodle to walk, I began to believe in my own infallibility, and I prepared a terrific development program for him, unknown to Mama and Daddy, of course.
However, Doodle is unable to keep up with his brother, eventually dying from his efforts when he is pushed too hard.
Doodle is a burden in the sense that he cannot fulfill the expectations of his brother, no matter how hard the brother tries to help him develop physically. In the end, Doodle remains a burden even after his death, as the brother must live with the guilt of pushing him too hard and not accepting him for what he is.