Zenaida and Philonella were sisters, born into a well-educated Jewish family and said to be cousins of Paul the Apostle. They were instructed and baptized into the Christian faith by their brother Jason, who was bishop of their native city of Tarsus. On entering the philosophical academy at Tarsus, they devoted themselves to the study of medicine, and when they completed their studies moved to the mountains around Pelion near Demetriada in Thessaly. This was a region renowned for its healing springs and shrines to Asclepius. The physicians who practiced there catered to the wealthy, charging exorbitant amounts for their services, and augmented their incomes with the sale of magical amulets and charms.