Francis and Yolande had a son, Renaud, Count of Montfort. Renaud died young and Yolande died in 1440. Francis and Isabel had two daughters:
Margaret of Brittany (1443–1469, Nantes), married Francis II, Duke of Brittany
Marie of Brittany (1444–1506), married John II, Viscount of Rohan and Count of Porhoët.
Francis I died in 1450.