This scene is the audience's first encounter with Sebastian, and it serves a crucial dramatic function: confirming that Viola's twin is alive and setting up the mistaken identity plot that will drive the play's final acts. Shakespeare carefully mirrors Scene 2 of Act I — both twins wash ashore, both grieve for the other, and both are aided by loyal companions. This structural symmetry reinforces the play's fascination with doubles and reflections.
Sebastian's grief for Viola is genuine and affecting. His admission that he is "so near the manners of my mother" that his eyes will betray his tears connects grief with femininity in a way that parallels — and complicates — Viola's gender disguise. If Sebastian weeps like a woman, and Viola performs as a man, the play quietly asks what stable difference gender actually marks. The twins' emotional resemblance runs as deep as their physical one.
Antonio's devotion to Sebastian is one of the play's most intense emotional bonds. His language — "If you will not murder me for my love, let me be your servant" — carries a passionate urgency that many critics read as homoerotic, or at minimum as a friendship that transcends ordinary loyalty. Antonio will later risk his life and freedom for Sebastian, making him one of the play's most selfless characters. His willingness to enter Orsino's court despite "many enemies" establishes the danger that will erupt in Act III.
Sebastian's self-description introduces important dramatic irony. He tells Antonio that his sister "much resembled me" and was "of many accounted beautiful" — precisely the resemblance that will cause Olivia to mistake him for Cesario and fall into his arms. Every detail Sebastian shares about the twins' likeness is a seed planted for the comic confusions ahead.