In the early 1050s, two of the most powerful rulers of mid-eleventh-century north-western Europe met in the small county of Ponthieu, which lay between their two principalities, to conclude the marriage alliance which probably quite soon afterwards produced Robert ‘Curthose’, the subject of this biography. Count Baldwin V of Flanders brought his daughter Matilda, a ‘very beautiful and noble girl of royal stock’, to meet William, ruler of Normandy, who was accompanied by his mother, Herleva, and step-father, Herluin de Conteville. Matilda was probably in her mid to late teens, and her husband, William, was slightly older, perhaps twenty-one or twenty-two years of age. There is no evidence, however, that he was any more sexually experienced than his partner, as the contemporary sources record no premarital liaisons. Indeed, by the early twelfth century, stories were circulating that such was William's ‘respect for chastity, especially in early manhood, that public gossip told of his impotence’.

There is no reliable evidence as to any early affective bond between Robert's parents, although one version of the story of their courtship claimed that initially Matilda had rejected William's advances because she refused to marry a bastard. Determined to win her affection or at least her consent to marriage the duke made his way to Bruges and broke into her residence where he beat and kicked her. Not surprisingly Matilda took to her bed to recover, but she was apparently impressed or intimidated enough by this display to declare that she would marry no-one else. From Ponthieu, the wedding party proceeded to Eu and, after making various gifts, Count Baldwin formally handed over his daughter to her new husband and the nuptials were celebrated. William and his mother then conducted Matilda to the ducal capital at Rouen, ‘with the greatest ceremony and honour’. Robert's maternal lineage was illustrious for there was royal blood in Matilda's veins. Her mother, Adela, was the daughter of King Robert II ‘the Pious’ of France. Robert's maternal grandfather, Count Baldwin V, was recognised as a man of noble stock and considerable political influence. Even kings acknowledged Baldwin's influence and he had often challenged the Holy Roman Emperor in major wars, concluding them to his own advantage.