She was a daughter of Otto-William, Count of Burgundy[1] and Ermentrude de Roucy and a member of the House of Ivrea.

[1] After her husband's death, Agnes lost her influence at the court of Poitiers since her sons were not heirs.

The succeeding Count of Poitou was Agnes's son, Peter, who took the name of William VII Aigret.

The reasons are varied: the most logical is the absence of children, however the council of Reims in 1049 condemned certain marriages as incestuous and judged them to part; in addition, Geoffrey went to war against the King of France who appreciated the little freedom from war that would take his vassal to Germany (it seems that Geoffrey had to swear allegiance to the emperor and to no longer depend on the King of France) and it is very possible that the King imposed on his vanquished vassal that he should divorce his wife.

In 1058 William left for another war against his former stepfather Count of Anjou, probably because Geoffrey gave the dowry of Agnes to his new wife, Adelaide.

The young count had remained close to Geoffrey because he was the only father figure he knew and he reconciled with Anjou.

Agnes, despite her retirement, was still very active and did not hesitate to travel throughout Poitou to participate in donations or simply see her son at the court of Poitiers.