Peter I, Duke of Brittany French duke (1191–1250) Parents Yolande de Coucy Robert II, Count of Dreux Children Olivier Ier de Machecoul John I, Duke of Brittany Yolande of Brittany Siblings Philippa of Dreux Robert III, Count of Dreux Henri de Dreux Isabelle of Dreux Alix de Dreux Jehan de Braine Eleanor de Dreux Yolande de Dreux Agnes of Dreux Partners Alix, duchess of Brittany Marguerite de Commequiers, dite de Montaigu, Dame de Montaigu
