Joan FitzGerald's paternal grandparents were Thomas FitzMaurice FitzGerald and Rohesia de St. Michael, and her maternal grandparents were John de La Roche, Lord of Fermoy, and Maud de Waleys (Walsh).
Joan FitzGerald's paternal grandparents were Thomas FitzMaurice FitzGerald and Rohesia de St. Michael. Her maternal grandparents were John de La Roche, Lord of Fermoy, and Maud de Waleys (Walsh).