What is the purpose of Mama's telling of the death of "Daddy's brother" in "James Baldwin's story "Sonny's Blues"?

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dymatsuoka eNotes educator| Certified Educator

Mama tells about the death of "Daddy's brother" to bring home to the narrator the fact that the world is violent and brutal, especially for black people in America.  In response to Mama's request that he look out for his brother Sonny, the narrator responds that she needn't worry because Sonny is "a good boy and he's got good sense".  Mama points out that "it ain't only the bad ones, nor yet the dumb ones that get sucked under", and to emphasize the fact, she tells how Daddy's brother, who was "a fine boy", was run over and killed by a car filled with drunken white men while crossing a moonlit road one Saturday night.  Like Sonny, Daddy's brother was a musician, and had an especially vulnerable nature.  Mama wants the narrator to look after Sonny, and even if he "may not be able to stop nothing from happening" to at least "let him know you's there".