Hadmar first appeared in an 1125 deed, in the service of the Babenberg margrave Leopold III. He probably was the son of Nizzo, who served as a burgrave on the castles in Krems and Gars. While many sources refer to Hadmar as a (great-)grandson of legendary Azzo of Gobatsburg, more recent research has shown this to be incorrect.[1]
He is credited for the construction of Kühnring castle (in present-day Lower Austria), which became the ancestral seat of the Kuenring noble family. Hence, Hadmar was the first member of the dynasty to style himself "of Kuenring" from 1132 onwards. Hadmar also had Dürnstein Castle erected in his Wachau estates, where about sixty years later King Richard I of England was imprisoned after being captured near Vienna by Duke Leopold V of Austria.