In Pwyll Pendefig Dyfed, the first branch of the Mabinogi, Hefeydd Hen (or Heyfedd the Old) was the father of Rhiannon.
According to legend, Hefeydd Hen tried to force his daughter Rhiannon to be married against her will to Gwawl son of Clud. She met Pwyll of Dyfed at the Mound of Arberth), is mentioned as one of the Seven Knights left to take charge of the Island of Britain when Bran went to rescue his sister in the second branch of the Mabinogi.