Agnes was a daughter of Duke Otto I of Merania and Countess Beatrice II of Burgundy, a member of the Imperial House of Hohenstaufen.

Her younger sister Adelaide (d. 1279) married Count Hugh III of Chalon and succeeded her brother Otto as Countess of Burgundy.

Her husband, who was known as "the Quarrelsome",[2] had just divorced his first wife Eudokia Laskarina ("Sophia"), a daughter of the Byzantine emperor Theodore I Laskaris, due to childlessness.

The haughty Austrian ruler hurled himself into a fierce border conflict with King Béla IV of Hungary and was killed in the 1246 Battle of the Leitha River.

Ulrich could succeed Agnes' late husband as Lord in Carniola and became Carinthian duke upon his father's death in 1256.