Jim was a 15-year-old boy living with his little sister, Joy. Their parents had passed away long ago. Jim took care of Joy by himself. One day, Jim woke up at 3 in the morning as usual. When Joy was sleeping alone, Jim left their little house to deliver newspapers. As he did so, he found something unusual. One man was sitting in front of Jim's house. Jim was so surprised that he stopped to look at him closely. It was an icy morning and he looked very old. The poor old man didn't have anything to cover himself with. Jim went into his house to get the old man a blanket . However, there were no extra blankets, so Jim thought hard and took his father's coat. It was the only thing of his father's that he had left. Jim wrote a short note. "Sir, I found you sleeping in front of my house. This is my father's coat. I hope it fits you well." He put the note in a pocket of the coat, and covered the old man with the coat. Then he went to work. When he came back three hours later, both the man and the coat were gone. Jim thought that it was the best thing he could have done with his father's coat. That afternoon, Jim hurried home after school because Joy was at home alone. However, Joy and the old man were standing in front of the house, and Joy shouted to Jim, "Brother!He's our grandfather!" The grandfather smiled and said, "Jim, I have been looking for you all around the country for eight years. I'm not rich. But I can take care of you two. Thank you for giving me the coat and letting me know what a good person my grandson is. This coat was the very one that I gave my own son, a long time ago." Jim looked after his little sister by himself because   _  .
they were too poor their grandfather left them he was old enough their parents had died