Final answer:
Larry feels jealous because his father's return from war has shifted his mother's attention towards his newborn brother, Sonny. He used to receive his mother's full attention when his father was away, but now he feels neglected and excluded.
Step-by-step explanation:
Larry feels jealous because his father's return from war has shifted his mother's attention towards his newborn brother, Sonny. Larry was used to having his mother's full attention when his father was away, but now he feels neglected. Moreover, Larry notices that his father brings home gifts for his mother and brother, but not for him, which adds to his feelings of jealousy.