Gregory of Nyssa
Gregory Nazianzen wrote a letter of condolence on her death to Gregory of Nyssa in which Gregory Nazianzen mentioned "your sister Theosebia" and "true yoke-fellow of a priest". Hither comes the ambiguity of her identification. Some historians supposed Theosebia was the wife of Gregory of Nyssa, others suppose she was one of his sisters like Macrina the Younger. If so, then Theosebia was the sister of Basil the Great as well.