[2] Brychan was a son of Anlach, an Irish settler who had peacefully taken control of the area by marrying Marchell, the heiress of Garth Madrun.

Traditional Welsh accounts claim that Triffyn had gained his power by peaceably marrying Edynfed's heiress (they do not indicate whether this was under duress).

The power of Irish raiders, particularly the Uí Liatháin, grew increasingly strong, and was not weakened until it was reduced by the sons of Cunedda, as reported in the Historia Brittonum.

Rhiwallon succeeded due to the subsequent collapse of Powysian power, under pressure from Dogfeiling, and the extreme youth of Cynan's later successor.

[4] In the mid 8th century, Seisyll (king of Ceredigion) invaded, conquering Ystrad Tywi, and thus physically cleaving apart Dyfed and Brycheiniog.

[5] Rhain ap Cadwgan, great-grandson of Cloten and king of Dyfed-Brycheiniog, initially attempted to retain the union; the surviving parts were consequently known as Rhainwg.

Geoffrey of Monmouth identifies Gruffydd (as Grifud map Nogoid - i.e. Gruffudd ap Nowy) as one of the princes present at the coronation of King Arthur.

[9] Hwgan responded by seeking an alliance with the Danes, but died soon afterwards while defending Derby (a Danish-held city) from the Saxons.

[9] The earlier Anglo-Saxon Chronicle also reports these events, but without naming the Brycheiniog king, or mentioning his raid against Mercia; it was, though, Æthelflæd who defeated the Danes at Derby.

Many Welsh princes had been vassals or allies of the Saxon kings, so actively supported the rebellion of Eadric the Wild against the Norman presence in England.

This past behaviour of Welsh princes naturally made the Normans ill-disposed towards them when an anti-Norman revolt broke out in Northern England ten years later.

An undated charter of Bernard de Neufmarché mentioned "all the tithes of his lordship which he had in Brycheiniog in the woods and plains" (as well as Glasbury).

Rhys ap Hywel's second son was Einion Sais, who militarily supported the campaigns of Edward's son, King Edward III;[15] Einion's great-great grandson was Sir Dafydd Gam, an enemy of Owain Glyndŵr and hero of Agincourt, from whom descend the present Earls of Pembroke.