No. 3: Albert von Thurn und TaxisAge: 29
Net Worth: $1.5 billion
Albert II Maria Lamoral Miguel Johannes Gabriel, 12th Prince of Thurn and Taxis, is a German aristocrat. He has been listed as the world's youngest billionaire many times since his father's death in 1990. He is also active in GT racing, having competed in the German GT Championship in both 2007 and 2008, the FIA GT3 European Championship, and most recently this year's FIA GT World Championship. He has assets in a technological company and in the arts. He also has substantial real estate holdings, including 30,000 hectares of woodland in Germany.