Sefwlch
Son of Cleddyf Cyfwlch and brother of Cyfwlch and Bwlch.
Syfwlch was one of Arthur’s warriors. He was needed by Culhwch, as one of his tasks, to help hunt the boar Twrch Trwyth.
He had a sword named Gleisyad, a dog named Cabal, a horse named Llwyrddyddwg, a wife named Diasbad, a grandchild named Eissywed, a daughter named Gwaethaf Oll, and a maid named Gwaeddan.
See also
Carn Cabal | The Legend of King Arthur
Source
Culhwch and Olwen | Late 11th century