Count of Louvain

The Counts of Louvain were a branch of the Lotharingian House of Reginar which from the late 10th century ruled over the estates of Louvain (French) or Leuven (Dutch) in Lower Lorraine.

The Reginar count Gilbert of the Maasgau, a vassal of the West Frankish king Charles the Bald, had married a daughter of the Carolingian emperor Lothair I in 846; his son Reginar ruled over the Duchy of Lorraine (Lotharingia) from 910 to 915. His son and successor Gilbert swore fealty to the East Frankish king Henry the Fowler in 925 and three years later married his daughter Gerberga of Saxony. His younger brother Reginar attained the title of a Count of Hainaut.

About 990 Lambert the Bearded (d. 1015), grandson of Count Reginar II, married Gerberga, daughter of the Carolingian duke Charles of Lower Lorraine, and in 994 was vested with the title of Count of Louvain. Originally limited by the rivers Demer, Dijle and Velp, that is more or less the region known today as Hageland, his county rapidly increased in size and power. Lambert I incorporated the County of Brussels and in 1013 annexed the Duchy of Bruningrode, located around Tongeren.

...
Wikipedia