Aed Brosc was of the tribe of the Déssi who hailed from the County Waterford region of Ireland. His grandfather, Eochaid Allmuir (from Over the Sea) had left his homeland when a bid for independence by his people was severely crushed by their High-King. There is some evidence to suggest the Roman authorities asked for his help in keeping Irish pirates away from the Dyfed coast. His descendants in the area certainly used the Roman title of 'Protector' rather than king.
The descendants of Aed’s eldest son, Urb, eventually founded the Kingdom of Brycheiniog, while his younger son, Triffyn Farfog, married the heiress of the Dyfed Kings.... 1
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Irish raiders were causing the British widespread problems throughout the fourth and fifth centuries. To combat this a wandering sept of the Déisi tribe were probably settled in Demetia by Magnus Maximus to act as protectors of the coastline. Existing evidence confirms this by suggesting that the Roman authorities asked for the help of Aed Brosc in keeping Irish pirates away from the western coast of Britain. When the last British king died without a male heir, the Déisi were on hand to fill the breach. By this time they had become Romanised themselves, and soon became indivisible from their Western British (Welsh) subjects. 2
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The high number of memorial stones found with Irish (Ogham) inscriptions in south-west Wales, tells us that Dyfed was subject to substantial Irish settlement following the fall of Rome in Britain. In particular, Aed Brosc, of the Deisi tribe from the County Waterford region of Ireland played a major role in the foundation of the Kingdoms of both Dyfed and Brycheiniog. His grandfather, Eochaid Allmuir (from Over the Sea) had left his homeland when a bid for independence by his people was severely crushed by their High-King and left them homeless, and the descendants of Aed’s eldest son, Urb, eventually founded the Kingdom of Brycheiniog, while his younger son, Triffyn Farfog, married the heiress of the King of Dyfed. 3
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