Gwaldys soon had a son, the famous saint Cadoc. To celebrate his son's birth Gwynllyw went on another raid stealing cattle from Caerwent. When Saint Tatheus came courageously to demand the return of a cow, the King was so impressed he decided in return to send his son to Tathyw at Caerwent to be educated. Gwynllyw supposedly had other children, also saints: Cynidr, Bugi and Egwine. Bugi was married to Peren, daughter of King Lot/Llawdden/Greidal ap Arthwys. One, Maches (Latin: "Machuta"), the sister of Cadoc according to tradition, was killed by robbers who were stealing her finest ram. Tathan, to whom the murderers confessed their crime, built a church on the spot.