HERBERT II OF VERMANDOIS WAS A CRUCIAL ALLY of Robert I and Hugh
the Great in their struggles against the Carolingians. His progeny
included the counts of Flanders and of Blois-Chartres-Champagne and as
these lines endured it was difficult for the Capetians to contract
durable marriages with these families until the reign of Louis VII;
otherwise they were liable to dissolution for consanguinity. Hugh
Capet's marriage to Adelaide of Aquitaine had a similar effect.