Seymour was born in 1912 in Pietrokow, Poland. His father was a cantor.
After his son’s birth, the family moved to Lodz, Poland. There, Seymour, the child, studied in a religious elementary school and in a state-run school.
As a child he joined his brother Yankev and sister Helen in concerts, and he even appeared in one-man performances as a “wunderkind,” which is a term used to describe someone who is a child protégé.
Later, Seymour traveled throughout Europe, and in 1920 he came to America.
In December 1923, Secretary of State Charles Evans Hughes submitted a special law to the congressional committee on immigration that allowed young Seymour to remain in America with immigrant status. To further support this special request, he was asked to appear at the White House, and he did so on December 21, 1923, before President and Mrs. Calvin Coolidge in his role as a “wunderkind,” participating in a concert of Italian, English and Yiddish songs.
Shortly thereafter, Seymour appeared in concert in New York City traveling with the “Three Kids Circle” in an English-language act. Later he appeared as a child actor in the Lenox Theatre in Harlem.
In 1924 he made his debut as “Shaike” in Gershom Bader and Joseph Rumshinsky’s musical, “The Rabbi’s Melody” in the Second Avenue Theatre.
From that time on he was considered to be a legitimate actor.