Sometimes with the patronymic ap Cynyr or vab Cynyr [son of Cynyr]. A character in Welsh Arthurian stories, a companion of Arthur along with Bedwyr, Cei is also the seneschal of Arthur's household and has a personality composed of unequal parts of courage and buffoonery. In the early poetry, such as the 12th-century Black Book of Carmarthen, he appears to be a great and admirable hero. In the later romances, however, he descends into a surly steward characterized by cruel, sometimes ridiculous behaviour. Even in the later material he can still initiate action. He is clearly a model for Sir Kay in English Arthurian narratives. See also GLEWLWYD GAFAELFAWR.
See Rachel Bromwich, Trioedd Ynys Prydain, 2nd edn. (Cardiff, 1978), 303–7, 547.