As an adult, Cardozo no longer practiced Judaism (he identified as an agnostic), but he was proud of his Jewish heritage.

Of the six children born to Albert and Rebecca Cardozo, only his twin sister Emily married.
She and her husband did not have any children.

Constitutional law scholar Jeffrey Rosen noted in a The New York Times Book Review of Richard Polenberg's book on Cardozo:
Polenberg describes Cardozo's lifelong devotion to his older sister Nell, with whom he lived in New York until her death in 1929.
When asked why he had never married, Cardozo replied, quietly and sadly, "I never could give Nellie the second place in my life."
As an adult, Cardozo no longer practiced Judaism (he identified as an agnostic), but he was proud of his Jewish heritage.
Of the six children born to Albert and Rebecca Cardozo, only his twin sister Emily married. She and her husband did not have any children. 
Constitutional law scholar Jeffrey Rosen noted in a The New York Times Book Review of Richard Polenberg's book on Cardozo:
Polenberg describes Cardozo's lifelong devotion to his older sister Nell, with whom he lived in New York until her death in 1929. When asked why he had never married, Cardozo replied, quietly and sadly, "I never could give Nellie the second place in my life."
Benjamin N. Cardozo