He was a younger maternal half-brother of Marie de Champagne and Alix of France. He was a younger brother of William, Count of Poitiers, Henry the Young King, Matilda of England and Richard I of England. He was also an older brother of Leonora of Aquitaine, Joan of England and John of England.
King Henry arranged for Geoffrey to marry Constance, the heiress of Brittany. Geoffrey was invested with the duchy, and he and Constance were married in July 1181. Geoffrey and Constance would have three children, one born posthumously:
Geoffrey was a good friend of Philip Augustus of France, and the two statesmen were frequently in alliance against King Henry. Geoffrey spent much time at Philip's court in Paris, and Philip made him his seneschal. There is evidence to suggest that Geoffrey was planning another rebellion with Philip's help during his final period in Paris in the summer of 1186. As a participant in so many rebellions against his father, Geoffrey acquired a reputation for treachery. Gerald of Wales said the following of him: He has more aloes than honey in him; his tongue is smoother than oil; his sweet and persuasive eloquence has enabled him to dissolve the firmest alliances and his powers of language to throw two kingdoms into confusion.
Geoffrey also was known to attack monasteries and churches in order to raise funds for his campaigns. This lack of reverence for religion earned him the displeasure of the Church and also of the majority of chroniclers who were to write the definitive accounts of his life.
Geoffrey died on 19 August 1186, at the age of twenty-eight, in Paris. There are two versions of his death. The more common first version, is that he was trampled to death in a jousting tournament. At his funeral, a grief-stricken Philip was said to have attempted jumping into the coffin. Roger of Hoveden's chronicle is the source of this version; the detail of Philip's hysterical grief is from Gerald of Wales.
In the second version, in the chronicle of the French Royal clerk Rigord, Geoffrey died of sudden acute abdominal pain, which reportedly struck immediately after his speech to Philip, boasting his intention to lay Normandy to waste. Possibly, this version was an invention of its chronicler; sudden illness being God's judgement of an ungrateful son plotting rebellion against his father, and for his irreligiosity. Alternatively, the tournament story may be an invention, by Philip, to prevent Henry II's discovery of a plot; inventing a social reason, a tournament, for Geoffrey's being in Paris, Philip obscured their meeting's true purpose.
Geoffrey was buried at Notre Dame Cathedral.