On the death of her father (1222), her mother Mathilde de Courtenay assigned her the three counties for which she was responsible, Nevers, Auxerre and Tonnerre, from 1222 to 1225.
Agnes was the daughter of Hervé IV, Baron of Donzy, and Mathilde de Courtenay.
[1] Her mother was the only child from the first marriage of Peter II of Courtenay and Countess Agnes I of Nevers, of whom she was the heiress.
With this union, King Philip II of France, grandfather of the young groom, hoped to attach the French counties of Nevers, Tonnerre and Auxerre to his crown.
[4] Their orphaned children were entrusted to their maternal grandmother, Mathilde de Courtenay, Countess of Nevers.