Nello's mother Mary Daas perished in an Ardennes blizzard while traveling to her father Jehan Daas's home when Nello was about two, leaving the child orphaned. Before succumbing to exposure and exhaustion, she exacted Jehan's promise to raise Nello. This death led to Nello's upbringing by Jehan in profound poverty near Antwerp.

Mary possessed significant artistic talent, inherited by Nello and becoming a defining characteristic of his aspirations. The 1999 film adaptation reveals she studied under artist Michel La Grande, with whom she had a romantic relationship; Michel was Nello's biological father, a fact Mary concealed to avoid scandal.

Mary's legacy endures through Nello's artistic pursuits and his emotional bond to her memory. Jehan consistently reassured Nello of her enduring spiritual presence and their promised reunion after death. This concept culminates in a near-death vision where Mary, alongside Jehan and Peter Paul Rubens, welcomes Nello into a heavenly realm, signifying familial reconciliation beyond mortality. Her character remains foundational to Nello's origins and the narrative's themes of loss, artistic inheritance, and spiritual continuity.