Rivallon also had a sister Imogen who was married to a knight of Alan III of Brittany -- a man she completely dominated, becoming the eventual guardian of their son Brien.
Hamo I also had a natural son Saloman who was the given the fief of Garclip later known as the seigneurie of Du Guseclin.
Rivallon married Aremburga du Puiset, the daughter of Evrard, Count of Bretueil.
Before William had become Duke, the Breton tribal lands of the Cotentin Peninsula near Dol had been ceded to Norman rule.
Geoffroy's children have been identified as the Lord of Saint Berthevin La Tanniere, Hemenare, l'Ernee, Levare and Buron.