The couple had one son: Gero II, who in 993 would succeed Thietmar's brother, Odo, as Margrave of the Saxon Eastern March.

[citation needed] In 951, he was first recorded when he succeeded his father as margrave in the Gau Serimunt.

After the death of his uncle Gero the Great in 965, Thietmar inherited large parts of whose vast Marca Geronis and upon the death of Margrave Wigbert (before 976) received the Margraviate of Meissen from the hands of Emperor Otto II.

[citation needed] On 29 August 970, Margrave Thietmar and his brother Gero of Cologne founded the abbey of Thankmarsfelde,[1] which between 971 and 975 became a royal monastery.

His widow Swanehilde married Rikdag's successor Margrave Eckard I of Meissen.