Agnes was the daughter of Heinrich von Kottwitz but her mother is unknown. The date and place of her birth have not been found.
Her husband was Rudolf von Tautenburg. They were married, but the date and place have not been found. Their four known children were Rudolf (c1364-1425), Busso (c1366-1426), Apel (1369-1418) and Ulrich (1371-1429).