In 1031, Matilda was born into the House of Flanders. the second daughter of Count Baldwin V of Flanders and Adela of France. Flanders was of strategic importance to England and most of Europe as a "stepping stone between England and the Continent" necessary for strategic trade and for keeping the Scandinavian Intruders from England. In addition, her mother was the daughter of Robert II of France. For these reasons Matilda was of grander birth than William, who was illegitimate, and, according to some suspiciously romantic tales, she initially refused his proposal on this account. Her descent from the Anglo-Saxon royal House of Wessex was also to become a useful card. Like many royal marriages of the period, it breached the rules of consanguinity, then at their most restrictive (to seven generations or degrees of relatedness); Matilda and William were third-cousins, once removed. She was about 20 when they married in 1051/2; William was some four years older, and had been Duke of Normandy since he was about eight (in 1035).