Where did Scrooges nephew live?

Answer 1

Its not specifically mentioned in the original book but its assumed he lived near the city of London within a walking distance of Scrooges own home

Answer 2

Scrooge's nephew, Fred, lived in a house in a pleasant part of the city, likely not too far from Scrooge's office. He invited Scrooge to his Christmas dinner every year despite his uncle's curmudgeonly behavior.