In Flannery O'Connor's "A Goodman is Hard to Find," we meet the Misfit whose personality is revealed to us through his interaction with primarily one character: the grandma. Both the format and themes of this story are reminiscent of previous stories.
Here is an example: the grandma, a selfish lady obsessed with class rank, feels her mortality at the end of the gun and changes into a sweet, loving woman. Sound familar? Anyone remember Gabriel listening to the snow fall in Joyce's "The Dead" after dumbing down his speech for those of "not the same cut of class" as him?
Refocus from the grandma to the grandma and the Misfit, and we have two characters who foil each other because one, the grandma, is very basic and ordinary; whihle the Misfit is philisophical and enigmatic. How about that one? Any guess? The Sonny and his brother share the same qualities. Additionally, the format of "A Goodman is Hard to Find" and "Sonny's Blue", besides the jazzy synocopation, is similar--the characters personalities are communicated to us through the mutal interaction with another that foils them.
While calling it an obsession with death may be too strong, contemplation of one's finiteness seems only natural, and what better way to do it through conversations of two opposities (Plato did something like this, too, right?).
While the topics addressed are almost more stimulating than examining the character relationships and story structure, it is interesting that such diverse stories from different time periods (1914, 1955, 1957) all ask fundamental questions with similar methodology.