In 'Twelfth Night', what is the name of the lady Olivia's uncle?

In “Twelfth Night,” Lady Olivia’s uncle is Sir Toby Belch.

Sir Toby is Olivia’s lively, hard-drinking relative and one of the play’s principal comic figures. He stays in Olivia’s household while she is mourning her brother, but he rejects her strict, melancholy atmosphere in favour of late-night drinking, singing and practical jokes. His name itself suggests his fondness for excess.

Sir Toby is closely associated with Sir Andrew Aguecheek, whom he encourages to pursue Olivia even though Sir Andrew is foolish and unlikely to win her. Sir Toby also helps Maria devise the forged-letter trick that humiliates Olivia’s steward, Malvolio. That subplot is comic, but its cruelty has made Malvolio’s treatment one of the play’s most debated elements.

A common mix-up is to choose Malvolio, because he is a prominent member of Olivia’s household, or Sir Andrew, because he is Sir Toby’s companion. Neither is Olivia’s uncle: Sir Toby is the family relation, while Sir Andrew is a visiting knight and Malvolio is the steward.