Two entries with the name Regin.

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Regin

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According to Geoffrey of Monmouth, a king of Britain in the third or second century BC.

He was the son of King Gorbonian. He succeeded his uncle, King Elidur, ruled in justice and mercy, and was succeeded by his cousin Margan.

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Source
Historia Regum Britanniae | Geoffrey of Monmouth, c. 1138

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Regin

Regan, Regian, Regeym

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An Arthurian knight, appearing in Geoffrey of Monmouth, who was the son of Abudar or Claud.

Welsh mythological genealogies mention a Regin who had a grandfather named Cloten.

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Sources
Historia Regum Britanniae | Geoffrey of Monmouth, c. 1138
Roman de Brut | Wace, c. 1155

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