Robert I "The Magnificent" of Normandy
Succeeded his brother Richard III to the duchy and reigned from 1028-1035.
william the conqueror's mother Arlotta was a peasant girl, daughter of a tanner of falaise. She had another illegitimate child, Adelaide, whose three marriages were all to nobles. After her liaison with Duke Robert, she was then married off to Herluin and became the Viscountess and had a son Odo of Bayeux, who aided his half-brother William in his battles and in governing England.
Richard I "The Fearless" of Normandy (3rd Duke)
His daughter Emma wed two English Kings, first Ethelred and second, Canute; two of her sons, Hardecanute and Edward the Confessor became King of England.
William of Normandy (2nd Duke)
reign from 917-942
The Dane Rollo (Hrolf) (1st Duke)
Rollo was Norwegian; he repeatedly attacked the shoe of England and fought King Alfred's forces. he then crossed the Channel and sailed up the Seine toward Paris, laying waste whatever was in his path. He and his marauding Norsemen settled along the river and the northwestern coast of what is now France, giving the area its name Normandy.
The Frankish King, Charles the Simple (879-929), a great-great grandson of Charlemagne, after 20 or 30 years recognized that the Norsemen were there to stay. Rollo agreed to accept Christianity and acknowledged the suzerainty of Charles, and in 912 he was made Duke of Normandy and formally granted the fief upon which he and his Norsemen had be settled for years.