FAMILY RELATIONSHIP
Fan is the mother of Scrooge's nephew, as stated by the Ghost and confirmed by Scrooge.
FAN
'She died a woman,' said the Ghost, 'and had, as I think, children.' 'One child,' Scrooge returned. 'True,' said the Ghost. 'Your nephew!' Scrooge seemed uneasy in his mind, and answered briefly, 'Yes.'