Fan was Scrooge's younger sister and Fred's mother, and she died when she was a young woman. During his journey with the Ghost of Christmas Past, Scrooge is forced to confront his memories of his beloved sister. A true embodiment of youthfulness and kindness, Fan “had a large heart,” and always treated Scrooge with warmth and love. After their father sent Scrooge away, it was Fan who convinced their father to allow Scrooge to return home. She then traveled to tell Scrooge the news and welcome him back home, warmly embracing him and declaring, “We’re to be together all the Christmas long, and have the merriest time in all the World.”

Fan provides vital insight into Scrooge's childhood, a time before he became hardened and selfish. The memory of Fan and Scrooge humanizes Scrooge for the first time and offers a contrast to his current loveless, solitary existence. The reader learns that Scrooge was not always so cruel and unfeeling. There was once a time when he was loving and affectionate. The scene with Fan also serves to generate sympathy for Scrooge. He evidently had a difficult, neglectful childhood, and lost the one person who was clearly a beacon of hope and affection for him. It’s possible Fan's untimely death has partly contributed to Scrooge's withdrawal and unwillingness to make connections with others. 

The memory of Fan also forces Scrooge to confront his guilt and consider the kind of person he has become. After being reminded of Fan's warmth and kindness, "Scrooge seemed uneasy in his mind." He undoubtedly feels remorseful for his treatment of Fan's son, Fred. Scrooge is unkind to Fred and does not treat him like family. His cruel treatment of Fred contrasts starkly with Fan’s loving treatment of Scrooge. Memories of Fan force him to revisit his past and address his guilt, thus setting the stage for his eventual redemption.