When his father left the duchy to fight Hugh Capet for the throne of France in 987, he became regent in Lower Lorraine when still apparently under twenty. Charles was defeated definitively in 991 and died two years later a prisoner in Orléans. Otto then succeeded into the full dukeship. In 1002, at the death of the Holy Roman Emperor Otto III, he was one of the loyal nobles who accompanied his body from Paterno to Aachen. According to the Chronica of Sigebert de Gembloux, he died in 1006, but he seems to be alive as late as 1012, when Count Godfrey II of Verdun succeeded to the duchy.
His wife is unknown, he had no son.
Otto was one of the last legitimate male-line descendant of Charlemagne and thus the Carolingian dynasty. His cousin, Arnulf, archbishop of Rheims, was illegitimate. The counts of Vermandois were direct male-line descendants of Charlemagne through Bernard, king of Italy, illegitimate son of Pepin of Italy. Although Otto was seemingly the last legitimate Carolingian, there remained illegitimate male lines, possibly also others than just the Vermandois.