The billionaire's family fund is surprisingly concentrated.Stanley Druckenmiller is often known for working closely with George Soros to "break the bank of England" when they shorted the pound and crashed it in 1992.However, Druckenmiller is a highly accomplished investor in his own right, and his Duquesne Capital Management fund is one of the best-performing funds in history. It grew from $1 million in 1981 to $23 billion by the time he closed it in 2010, generating an average annual return around 30%. Tod ...