Robert Curthose - the eldest son (c1054- 3 February 1134). In 1077 he rebelled against his father by attempting to take the castle of Rouen. He and his followers were not successful and he took refuge in Flanders. In 1080 a truce existed between father and son and Robert and Robert returned to the court until the death of his mother in 1183. He then travelled throughout Europe. On the death of his father in 1087 Robert inherited the title of Duke of Normandy while his younger brother, William Rufus became king of England. An agreement is reported to have been made by the brothers to be each other's heir. Circumstances changed however when some of the barons supporting Robert unsuccessfully rebelled against William in 1088. In 1096 Robert left for the Holy Land on the First Crusade. When king William died in August 1100 Robert was on his way back from the Crusade. In the meantime his younger brother Henry had become king. In 1101 Robert landed at Portsmouth pressing his claim to the throne but was defeated. Although he renounced his claim to the throne his continued involvement in disturbances resulted in Henry invading Normandy and in 1106 claiming Normandy as a possession of England. Robert was captured and held at Devizes Castle for twenty years before moving to Cardiff Castle where he died in 1134. He was buried at Gloucester Cathedral.
Robert married Sybilla of Conversano and had one legitimate son, William Clito born 25 October 1102 as well as three illegitimate children (two sons and a daughter). William's attempts to win back Normandy in 1119 and 1125 failed and he died in 1128 leaving no heir.