Also known as 'The Devil', Robert was the Duke of Normandy from 1027 to 1035. He was the second son of Richard II. He succeeded his brother Richard III, who was Duke for only one year, a fact that may indicate that Richard III may have been murdered. Robert was the father of William the Conqueror. William's mother was Herleva who Robert did not marry. Robert faced problems as soon as he succeeded his brother, facing conflicts with Robert of Rouen and Bishop Hugh of Bayeux, both churchmen who owned large amounts of land. He defeated Hugh and came to a compromise with Robert.

Robert was not slow in assisting both the French King Henry I, and the English monarchy in times of trouble. He gave refuge to Edward and Albert two brothers. Edward was to become 'The Confessor', and was to promise the English throne to Robert's son William. In 1035, Robert travelled to the Holy lands on pilgrimage but before he left, he made sure that William would become Duke of Normandy if he didn't return. He needed to have this confirmed, as William was illegitimate. As it was, Robert was killed returning from Jerusalem, and so the eight year old William became Duke. William's first years were in a duchy transformed by civil war after the death of Robert. Robert married Estrid, the half-sister of King Canute.

 Robert (I, Duke of Normandy 1027-35) ( - d.1035)
    +Herleva
    |   = William (I, the Conqueror, King of England 1066-1087) (b.1028 - d.1087)
    |       +Matilda (of Flanders) (b.1031? - d.1083)
    |           = Robert (II, Duke of Normandy 1087-1106) (b.1051? - d.1134)
    |           |   +Sybilla (of Conversano)
    |           |       = Clito, William ( - d.1128)
    |           = Richard (Son of William the Conqueror) ( - d.1081)
    |           = William (II, Rufus, King of England 1087-1100) (b.1057 - d.1100)
    |           = Henry (I, King of England 1100-1135) (b.1068 - d.1135)
    |           |   +Matilda Edith (of Scotland) (b.1080? - d.1118)
    |           |   |   = William (Adelin) (b.1103 - d.1120)
    |           |   |   = Matilda (Empress Maud) (b.1102 - d.1167)
    |           |   +Adeliza (of Louvain) (b.1103 - d.1151)
    |           |   +Corbet, Sybilla (Lady of  Alcester)
    |           |       = Sybilla (of Normandy) (b.1092? - d.1122)
    |           = Cecilia (Daughter of William the Conqueror)
    |           = Constance (of Normandy) (b.1066? - d.1090)
    |           = Adela (of Normandy) (b.1067? - d.1137)
    |               +Stephen (count of Blois) (b.1045? - d.1102)
    |                   = Theobald (V)
    |                   = Stephen (of Blois, king of England 1135-1154) (b.1100 - d.1154)
    |                   = Henry (of Blois, Bishop of Winchester) (b.1096? - d.1171)
    +Estrid

Mistresses are shown in italic