[1] William was a member of the House of Traungau, who had possessions in Salzburggau, Isengau and Sundergau; he is considered the founder of the noble Bavarian Wilhelminers family.
With the Ordinatio Imperii of 817, Louis II the German became king of Bavaria and immediately began to build his ties within the Bavarian aristocracy by assigning prestigious positions to his supporters.
These donations included, respectively, some goods from Linz and Wels, some localities around the Perschling, the possession of Rosdorf on the Danube along with an area between the Aist and Naarn rivers.
His wife was Engilrat,[3] of the house of Adaluncs von Roning, one of the most illustrious families in Bavaria.
[4] After his death, William II and Engelschalk I inherited the Traungau and expanded the area under their control to the entire Eastern March,[1] which they received from Louis the German.