Dr. Sorens, 26, said the project reflected his upbringing in Houston as the son of a single mother who pulled herself out of poverty with help from relatives and a Christian charity.

The Democratic senator from Illinois reflects on life as the son of a black African father and white American mother.

He also explains why it was important to root Cal's story in his own life, so that - without being autobiographical - it reflects his own history as the son of a Greek immigrant family which settled in Detroit.