In 19th century Belgium, a boy named Nello becomes an orphan at the age of two when his mother dies in the Ardennes. His grandfather Jehann Daas, who lives in a small village near the city of Antwerp, takes him in.
One day, Nello and Jehann Daas find a dog who was almost beaten to death, and name him Patrasche. Due to the good care of Jehann Daas, the dog recovers, and from then on, Nello and Patrasche are inseparable. Since they are very poor, Nello has to help his grandfather by selling milk. Patrasche helps Nello pull their cart into town each morning.
Nello falls in love with Aloise, the daughter of Nicholas Cogez, a well-off man in the village, but Nicholas doesn't want his daughter to have a poor sweetheart. Although Nello is illiterate, he is very talented in drawing. He enters a junior drawing contest in Antwerp, hoping to win the first prize, 200 francs per year. However, the jury selects somebody else.
Afterwards, he is accused of causing a fire by Nicholas (the fire occurred on his property) and his grandfather dies. His life becomes even more desperate. Having no place to stay, Nello wishes to go to the cathedral of Antwerp (see Rubens' The Elevation of the Cross and The Descent of the Cross), but the exhibition held inside the building is only for paying customers and he's out of money. On the night of Christmas Eve, he and Patrasche go to Antwerp and, by chance, find the door to the church open. The next morning, the boy and his dog are found frozen to death in front of the triptych.

Question: Why does Nello go to live with his grandfather?
Answer: His parents die, leaving him an orphan.
Alternative answer: His mother died when he was 2.