What is Harold Krebs' most important relationship in "Soldier's Home"?

Harold Krebs is the main character of Ernest Hemingway's short story "Soldier's Home." He has recently returned from Europe where he participated in some of the most important battles of World War I. Judging by the narrator's description of Krebs, he most likely suffers from what was then called "shell shock" and is now more commonly referred to as Post-Traumatic Stress Disorder. As a result of this he is portrayed as basically anti-social. He complains...

Harold Krebs is the main character of Ernest Hemingway's short story "Soldier's Home." He has recently returned from Europe where he participated in some of the most important battles of World War I. Judging by the narrator's description of Krebs, he most likely suffers from what was then called "shell shock" and is now more commonly referred to as Post-Traumatic Stress Disorder. As a result of this he is portrayed as basically anti-social. He complains that no one cares to listen to his true stories about the horrors of war and so he sinks to lying in his description of his experience. He doesn't seem to have any close friends, just acquaintances at the local pool room, and it is suggested that his relationship with his mother deteriorates after his return from the war. He even tells her that he doesn't love her and that he cannot pray with her.

The only other person he speaks to is his sister Helen, who obviously looks up to Harold and demands to know if he is her "beau." Their association is pivotal to the story because she seems to be the one who will ultimately bring Krebs out of his depression. In what appears to be an unimportant conversation, she tells him that he doesn't love her unless he comes to see her play indoor baseball. During the conversation he appears apathetic and noncommittal, but after an agonizing confrontation with his mother about his future he decides he will go see Helen play baseball. This implicit admittance that he can actually love someone is symbolically his first step to sanity and the leading of a productive life. Without his relationship with his sister Helen, it could be argued that Krebs would continue his lethargic and meaningless lifestyle.