Higgins was born in Melbourne, Victoria, to Christopher Higgins, an English-Australian general practitioner, and Margaret (née Morrison), an Australian childcare centre operator. Her sister, Nicola, is seven years older, and brother, David, is six years older. She learned to play classical piano from age six, following in the footsteps of Christopher and David, but realised she wanted to be a singer at about 12 when she appeared in an Armadale Primary School production of Andrew Lloyd Webber's musical Joseph and the Amazing Technicolor Dreamcoat. Bored with practice, she gave up playing piano at that time. Hoping for more freedom, she urged her parents to send her to Geelong Grammar School, an independent boarding school attended by her siblings. At Geelong she took up the piano again, this time playing jazz including performing with her brother David's group on weekends. She was introverted and found that piano practice helped her cope with living at boarding school.