Avesnes

The House of Avesnes took its name from Avesnes-sur-Helpe in northern France and rose through the inheritance of Hainaut. In 1212 Bouchard d'Avesnes married Margaret II, countess of Flanders and Hainaut; the disputed marriage pitted his children against the Dampierre children of her second marriage in the long Flanders-Hainaut succession war.

Louis IX's 1246 arbitration gave Flanders to the Dampierres and Hainaut to the Avesnes; John I of Avesnes made good his claim at West-Capelle in 1253, keeping Valenciennes as his seat. By the early fourteenth century the family also held Holland and Zeeland.

In 1337 William II succeeded his father as count of Hainaut, Holland and Zeeland; his sister Philippa was Edward III of England's queen, and he fought for England in France, taking part in the 1339 siege of Cambrai, granting Rotterdam its city rights in 1340 and capturing Utrecht in 1345. Later that year he fell fighting the Frisians at Warns, childless. His sister Margaret, wife of Emperor Louis IV, inherited the three counties, ending the Avesnes line.