Amon married St. Anna of Oxenhall, the probable widow of Lord Cynyr Ceinfarfog (the Fair Bearded) of Caer-Goch in Dyfed. He moved to his wife's rich estates and became an important official at the royal court, under King Aircol Lawhir. Anna had had several children by her first marriage who had since flown the nest; but Amon, somewhat her junior, was keen to have his own offspring. His brother, Umbraphel, had married Anna's sister some years previously and the two already had three children, but Amon's wife could not conceive. The newly-weds decided to visit a local holyman and, happily, his advice led to the birth of a son who they named Samson.

In later life, Amon fell ill and called for his son, Samson, to visit him. Samson tended his father back to health and persuaded him and most of the family to join him in entering the monastic life. Amon accompanied his son back to his monastery at Ynys Byr (Caldey Island). Later, he lived the life of a hermit on the Severn Estuary before Samson appointed him Abbot of Southill in Kernow (Cornwall). In extreme old age, he retired to the great monastery at Llantilltud Fawr where he eventually died and was buried.