Isabella's maternal grandparents were Charles VI of France and Isabeau of Bavaria.
Her paternal grandparents were John IV, Duke of Brittany and Joan of Navarre.
Isabella of Valois was married to Henry's predecessor, Richard II of England.
On 1 October 1430, at Redon, Isabella married Guy XIV de Laval.
Her husband remarried after her death, to Françoise de Dinan, widow of Isabella's younger brother Gilles, Lord of Chantocé.