Cornelia Cohen was the second born of the eleven children of Leah Lazarus and Mordecai Cohen of Charleston. However, her older sister Eliza died at age eleven, which made Cornelia the oldest child in the family to survive to adulthood.

Cornelia’s mother came from a well established though financially challenged Sephardic family, but her father was an astute Polish immigrant peddler who quickly made his way into a fortune. By the time Cornelia was grown, the Cohen family owned a plantation on the Ashley River. Cornelia and her siblings were brought up in a three and half story brick house on Charleston’s Broad Street.

Cornelia married late, for the period, at age 35, when she became the wife of her mother’s younger brother, Benjamin. Due to the large number of children in that generation of the Lazarus family, it happened that Benjamin was just five years older than Cornelia, and the two were thus closely matched in age. Benjamin and Cornelia had six children whom they raised in Charleston.