Siawn

Son of Iaen and brother of Sulyen, Bradwen, Moren, Teregud, and Caradawg. He came from Caer Dathal and was one of Arthur’s warriors.

In Bonedd y Arwyr he is, together with his brother Cradawc (Caradawg), said to be related to Arthur through his sister's marriage to Arthur. They are called gwyr Kaer Tathal ('men of Caer Dathal').