William faced several challenges on becoming duke, including his illegitimate birth and his youth: the evidence indicates that he was either seven or eight years old at the time.
Vilhelm stod over for adskillige udfordringer, da han blev hertug, bl.a. at han var uægte barn og at han var meget ung; det tyder på, at han var enten 7 eller 8 år gammel på dette tidspunkt.