[a] Geoffrey was the son of Duke Conan I, by his marriage to Ermengarde-Gerberga of Anjou.
[2] He was the grandson of Judicael Berengar, Count of Rennes.
When Geoffrey succeeded to Brittany he had several problems: In 996, at about the age of sixteen, Geoffrey entered into a dynastic alliance with Richard II, Duke of Normandy,[3] with a diplomatic double marriage between the two houses.
The church-sanctioned marriage ceremonies were held at Mont Saint-Michel, on the Breton-Norman border, and while Geoffrey married Hawise of Normandy,[4] daughter of Richard I of Normandy and sister of Richard II.
Richard married Judith of Brittany, Geoffrey's sister.