What year did Otto I, Holy Roman Emperor's mother become Duchess of Saxony?
Otto I, Holy Roman Emperor Otto I (23 November 912 – 7 May 973), traditionally known as Otto the Great (German: "Otto der Große" ), was German king from 936 and emperor of the Holy Roman Empire from 962 until his death in 973. He was the oldest son of Henry I the Fowler and Matilda.
Sophia I, Abbess of Gandersheim Sophia I (September 975 – 30 January 1039), a member of the royal Ottonian dynasty, was Abbess of Gandersheim from 1002, and from 1011 also Abbess of Essen. The daughter of Emperor Otto II and his consort Theophanu, she was an important kingmaker in medieval Germany.