Best small world story I ever came across was in a
profile of Richard Madeley in The Guardian a few weeks back:
Richard Madeley embarks on a family history that could be lifted straight from a Thomas Hardy novel. We begin in the early 20th century with his great-grandfather, Henry Madeley.
The impoverished Henry was desperate to emigrate from England to Canada with his wife and seven children, and make a new start, but they did not have the money. In 1907, Henry approached his brother William, a farmer, for financial help. William, who was unmarried, told him he would give him the money on one condition - Henry should give him his 10-year-old son, Geoffrey, to work on the farm in Shawbury, just outside Shrewsbury. When Geoffrey woke up one morning, his parents and six brothers and sisters were nowhere to be seen. They had left for Canada without a word.
In 1917, Geoffrey enlisted and was sent to the trenches. On the way to the south coast, his train pulled up at Crewe alongside a train full of Canadian soldiers. He wondered whether his brothers, whom he'd not seen for a decade, could be on the train, scoffed at the idea, but went to look anyway. Of course, he found them.