 Robert was the second son of Robert I de Grantmesnil and Hawisa d'Échauffour, daughter of Giroie, Lord of Échauffour.His family was from Calvados, arrondissement of Lisieux, in the canton of Saint-Pierre-sur-Dives.As a child he applied himself to learning and came to be known for his retentive memory and seemed to be destined for the church.