Rhain was king of Dyfed

Kingdom of Dyfed

The Kingdom of Dyfed is one of several Welsh petty kingdoms that emerged in 5th-century post-Roman Britain in south-west Wales, based on the former Irish tribal lands of the Déisi from c 350 until it was subsumed into Deheubarth in 920. In Latin, the country of the Déisi was Demetae, eventually to...

 and Brycheiniog

Brycheiniog

Brycheiniog was a small independent petty kingdom in South Wales in the Early Middle Ages. It often acted as a buffer state between England to the east and the powerful south Welsh kingdom of Deheubarth to the west. It was conquered and pacified by the Normans between 1088 and 1095, though it...

 in southern Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

 in the first half of the 8th century. The previous king of Dyfed, Rhain's father Cloten

Cloten of Dyfed and Brycheiniog

Cloten was the king of Dyfed and Brycheiniog in southern Wales. Already the king of Dyfed, he married Princess Ceindrech of Brycheiniog c.650, briefly uniting the two kingdoms; they would be divided again after his son's reign....

, had married the princess of Brycheiniog, briefly uniting the two kingdoms. During Rhain's rule, Seisyll

Seisyll

Seisyll ap Clydog was King of Ceredigion in Wales some time in the late 7th or early 8th century. He gave his name to the later kingdom of Seisyllwg, which consisted of Ceredigion plus the region known as Ystrad Tywi; as such he was possibly the king responsible for the expansion...

, king of Ceredigion

Kingdom of Ceredigion

The Kingdom of Ceredigion was one of several Welsh kingdoms that emerged in 5th-century post-Roman Britain. Its area corresponded roughly to that of the modern county of Ceredigion. The kingdom's hilly geography made it difficult for foreign invaders to conquer. Cardigan Bay bordered to the west...

, invaded Dyfed and conquered Ystrad Tywi

Ystrad Tywi

Ystrad Tywi is an area of south-west Wales situated on the banks of the Tywi river as it approaches the sea to join the Bristol Channel at Carmarthen...

 around 710. Ceredigion and Ystrad Towi were merged to form Seisyllwg. Sometime after this, the reduced Dyfed and Brycheiniog were briefly called Rhainwg.

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