Conan IV of Penthièvre "the Young" Duke of Brittany

Conan was son of Alan the Black, 1st Earl of Richmond and Bertha of Brittany, born after 1137. Grandson of Stephen, Count of Tréguier and Hawise de Guingamp, Conan III of Brittany and Maud, the illegitimate daughter of King Henry I of England. Conan was also the great great grandson of Duke Geoffrey I and great grandson of Eudes of Brittany.

Conan was the husband of Margaret de Huntingdon, the daughter of Henry of Scotland and Ada de Warenne and cousin of King Henry I of England. They married in 1160 and had one daughter, Constance, who would marry Geoffrey Plantagenet.

He was his mother's heir as the daughter of Duke Conan III, and she was the last member of the Breton House of Cornouaille to reign over Brittany. Conan and his daughter, Constance, would be the last of the Penthièvre dynasty in Brittany.

Conan's father died in 1146, his mother in 1156, but his step-father, Odo, the Viscount of Porhoet, denied Conan his ducal throne and rights. Within the year Conan IV was able to capture and imprison Odo, and claim his inheritance.

When Geoffrey VI, the Count of Anjou died in 1158, Conan seized Nantes, reuniting his Duchy once again. Then Geoffrey's brother, King Henry II of England, seized Conan's paternal inheritance the Earldom of Richmond, demanding the return of Nantes. Conan and Henry made peace, and Conan married Henry's cousin.

The Breton barons rebelled against Conan, King Henry exerted more direct rule of Brittany, forcing Conan to abdicate and give Brittany to his daughter. Once she was married to Geoffrey, she was no longer the Duchess, losing all control to Geoffrey as Duke.