Gwynfor Evans was born in Barry, near Cardiff, to Dan Evans and Catherine Richard. He had a brother named Alcwyn, and a sister named Ceridwen. His father ran a chain of shops in Barry, and his mother a china shop. His mother was a fluent Welsh speaker. As a boy, he was educated at Gladstone Road School. Later on he was educated at Barry County School, where he was captain of the school's cricket and hockey teams. The area was mostly English-speaking; at school he began learning the Welsh language, but did not become fully fluent until the age of seventeen.