The first name of Will’s aunt in the Banks household is Vivian.
Vivian Banks is Will Smith’s maternal aunt and Philip Banks’s wife in The Fresh Prince of Bel-Air. After Will is sent from West Philadelphia to live with the Banks family in Bel-Air, Aunt Viv becomes one of the adults guiding him through the sharp contrast between his old neighborhood and the Bankses’ affluent lifestyle.
Vivian is portrayed as intelligent, forthright and protective. She is also established as a career-minded woman, and the series gives her interests and ambitions beyond simply being the family’s mother. Janet Hubert played Vivian during the first three seasons, while Daphne Maxwell Reid took over the role beginning in season 4; both actresses played the same character, Vivian Banks.
The question asks for her first name, not the actress’s name or her married surname. That distinction explains why “Vivian” is the canonical answer. The other options are names from the wider show’s family and guest-character network: Viola is Will’s mother’s first name, while Janice and Helen are names associated with Vivian’s sisters in the series’ extended family.