The daughter of Cosmo Hamilton, Antonia comes to live with Penelope after her father passes away suddenly. Cosmo Hamilton is the love of Olivia Keeling's life, but she leaves her happy year in Ibiza with Cosmo and Antonia to return to her high-profile lifestyle in London. Cosmo never loves another woman like Olivia and Antonia maintains her close relationship with Olivia over the years. When Cosmo dies, Antonia has nowhere else to go since her mother has remarried a man she despises and thus ends up living with Penelope, whom she met when she came to visit Olivia in Ibiza.