He was the son of Dietrich of Haldensleben and a rival of the counts of Walbeck, one of whom, Werner, he succeeded in the march following his deposition.
Walbeck, Mansfeld-Südharz, a municipality in the Mansfeld-Südharz district, Saxony-Anhalt
•
Walbeck, Börde, a municipality in the Börde district, Saxony-Anhalt
Thietmar was a son of Siegfried the Elder, count of Walbeck (d. 15 March 991), and was related to the family of the emperor Otto the Great, and Kunigunde (ca. 956–13 July 997), daughter Henry I the Bald, Count of Stade (House of Udonids).