Answer:
The theme they share is indeed the inevitability of death.
Step-by-step explanation:
"The Love Song of J. Alfred Prufrock", by T. S. Eliot, revolves around the speaker's feeling of disillusionment and isolation. The speaker has accepted his own insignificance, his inability to connect with other human beings. The poem reveals the inevitability of old age and death. Prufrock repeats "I am growing old" as he sees life pass him by, death getting closer.
The same theme is found in the short story "The Jilting of Granny Weatherall" by Katherine Anne Porter. The main character is Granny Weatherall, an 80-year-old woman who is about to die. Granny, unlike Prufrock, has lived a rich life. She got married, raised her kids, worked hard... Still, death will happen for her just like it happens for everyone. Old age has come for her body, even if her heart is still young - and still preoccupied with the one man who left her.
There is nothing any of those two characters can do about death. No matter what kind of life they lived, they will both die, sooner or later. Therefore, the shared theme is the inevitability of death.