The origin remains unclear, however, Staufer counts are mentioned in a document of emperor Otto III in 987 as descendants of counts of the region of Riesgau near Nördlingen in the Duchy of Swabia, who were related to the Bavarian Sieghardinger family. A local count Frederick (d. about 1075) is mentioned as progenitor in a pedigree drawn up by Abbot Wibald of Stavelot at the behest of Emperor Frederick Barbarossa in 1153. He held the office of a Swabian count palatine; his son Frederick of Buren (c.1020-1053) married Hildegard of Egisheim-Dagsburg (d. 1094/95), a niece of Pope Leo IX. Their son Frederick I was appointed Duke of Swabia at Hohenstaufen Castle by the Salian king Henry IV of Germany in 1079.