Pierre Barniel is the widowed father of Annette and Daniel (Dani). His wife, Francine, died on Christmas Eve giving birth to Dani, leaving him solely responsible for raising their two children. Observing his young daughter Annette silently struggling under the weight of childcare and household duties, Pierre invited his elderly aunt, Claude Martha, to move in and assist with managing the home and caring for the children. Claude Martha became a maternal figure, bringing stability to the family.

Pierre consistently demonstrates care and support. He maintains kindness and understanding towards Lucien Morel, Annette's best friend, even after Lucien accidentally caused Dani's fall, which resulted in permanent leg injuries requiring crutches. This compassionate response contrasts with the original novel, where Pierre hated Lucien; in the anime, Pierre does not blame him for the accident. Pierre's rational and gentle nature acts as a stabilizing influence, especially during the family's hardships following Dani's injury.

Throughout the series, Pierre continues his role as a devoted father and widower, supporting his children emotionally while relying on Claude Martha's help for daily household management. His interactions focus on maintaining family well-being and mediating tensions, such as Annette's prolonged resentment toward Lucien.