Family
Guy IX was the son of Guy VIII de Laval and Isabelle de Beaumont-Gâtinais
In 1297 he married Béatrix de Gavre, countess of Falkemberg, only daughter of Rasès de Gavre.
Children:
- Guy X de Laval, who married Béatrix de Bretagne, daughter of Arthur II, Duke of Brittany, on 2 March 1315
- Rasès de Laval, lord of Morhem in Flanders, died after 1348, without known offspring
- Foulques de Laval, progenitor of the lords of Challouyau in Burgundy and Retz
- Pierre de Laval, bishop of Rennes, died 1357
- Jean de Laval, knight, lord of Passy-sur-Marne, who married Jeanne de Chemillé (died childless), and Aliénor Le Bigot de la Bérardière
- Isabeau (died 1322), who married Péan de La Roche-Bernard (died 18 June 1347 - Battle of La Roche-Derrien), Lord of Lohéac
- Catherine de Laval, wife of Gérard IV de Retz
- Jeanne de Laval, nun at Saint-Georges de Rennes.