Answer

Viola, twin sister to Sebastian. When disguised as a man, known as Cesario'
Orsino, Duke of Illyria, in love with Olivia
Olivia, a Countess
Sebastian, twin brother to Viola
Maria, a gentlewoman in Olivia's household
Sir Toby Belch, Olivia's uncle
Sir Andrew Aguecheek, a companion of Sir Toby's
Malvolio, steward to Olivia
Feste, a jester in Olivia's household.
Fabian, a member of Olivia's household.
Antonio, a captain, a friend to Sebastian.
Captain, a sea captain who helps Viola.
First Officer, an officer sent from Duke Orsino to arrest Antonio.
Second Officer, an officer who helps arrest Antonio.
Valentine and Curio, two gentlemen attending Orsino
Priest, a Holy Father
Musicians, Lords, Sailors, and other attendants