Clancy Sigal was the child of a love affair between two labor organizers, Jennie Persily and Leo Sigal. Jennie, a single mother, raised Clancy on her own, with a mostly absent father. After an army stint he worked as an entertainment agent. Sigal arrived as an immigrant in Great Britain, where he met and commenced a four-year affair with the writer Doris Lessing. He lived in Los Angeles with his screenwriter wife, Janice Tidwell, until his death.