Everything we know of Cynefrith is found in the Anonymous Life of Coelfrith, his brother. Here we learn (indirectly) that both Cynefrith and Coelfrith were kinsmen of King Oswine of Deira. It is clear that, following Irish fashion, Gilling was passed through blood relatives from its first abbot Trumhere, whom Bede describes as a close kinsman of King Oswine (HE III.24). Gilling was founded as penance (or weregeld) for Oswiu’s ordered execution of Oswine with the intention that the monks would pray for the soul of the victim Oswine and the murderer Oswiu.
The Anonymous Life of Coelfrith says that their father had held “a very noble office in the royal comitatus” (ch. 34). Given that Cynefrith was old enough to become abbot of Gilling within the first decade of its founding, the royal comitatus that his father participated in was probably that of King Oswine. If he had also served King Oswald before him, he may have been able to remain among the landed nobles, now elderly, under Oswiu — thanks in part of Oswine’s refusal to fight Oswiu. By preventing his thanes from engaging Oswiu in battle, Oswine may have allowed them to remain in fairly good standing with Oswiu. At least there wouldn’t have been blood debts to pay for Bernicians recently killed.
Ceolfrith’s Life tells us that he enters Gilling in c. 660 at about age 18 and that his brother Cynefrith had already turned over the abbacy to their kinsman Tunberht, who was the abbot who received Coelfrith. (The alliteration between the names Trumhere and Tunberht is hard to miss…) Now, we know that the first Abbot of Gilling, Trumhere became Bishop of Mercia in c. 658 and probably handed off the abbacy to a kinsman Cynefrith about that time, so Cynefrith’s term as abbot of Gilling was probably very short. The monastery had only been founded in c. 651.
According to the Life, “Cynefrith himself was lured away to Ireland, partly by his strong attraction to the study of Scripture and partly by his desire to serve the Lord in a freer manner with more opportunity for prayer and affectionate devotion.” It goes on to relate that not long after Coelfrith joined Gilling, his brother and others in Ireland died, probably in the plague that reached Ireland about 664. He may have been with the community of Lindisfarne-trained monks led by Egbert of Iona (including Chad and Aethelhun of Lindsey). When Coelfrith decides to set aside his duties as abbot of Wearmouth-Jarrow in 716, the Life asserts that he is imitating his brothers desire for a contemplative life and voluntary exile for the Lord.
This all suggests that the story of Coelfrith’s family, their nobility and his kinship with other notable figures was common knowledge in his monastery. Coelfrith and Cynefrith’s Irish trained origins may have also helped Wearmouth-Jarrow straddle the Irish vs Roman tensions in Northumbria. For example, if Chad had indeed been in Ireland with Cynefrith, this could have helped relations between Wearmouth-Jarrow and Lastingham.
I think Cynefrith is also the answer to a very important question at Wearmouth-Jarrow in their sorrow of 716-720, that is: why did he leave us? It is obvious from the Life of Coelfrith and Bede’s writings that his monks were extremely attached to him, and yet he left them. Belief that he was imitating his brother may have given them some comfort. Not having Ceolfrith’s grave as a continuing source of comfort must have cut them deeply. There seems little doubt that if they had his body they would have tried to establish his cause for sainthood. What does it tell us that Bede left a homily for the feast of Benedict Biscop, but not for Coelfrith?
Life of Coelfrith in Anglo-Saxon Saints and Heroes, Clinton Albertson, ed. Fordham University Press, c. 1967.