David (Chim) Seymour was born on November 20, 1911, in Warsaw, Poland. He had a sister, Eileen, who was three years older. Their parents were Regina and Benjamin Szymin, a respected publisher of Yiddish and Hebrew books. In 1914 David Seymour and his parents emigrated to Odessa just as World War I had begun. In 1919 they returned to Warsaw.