Georg Schaeffler

Georg Schaeffler and his mother, Maria-Elisabeth, own Schaeffler Group, one of the world's largest producers of ball bearings and machine components.

In 2009, he joined his mother. She'd been running Schaeffler after the death of her husband, Wilhelm, who founded the firm with his brother in 1946.

A year before, the company took over tire and auto parts giant Continental AG in a $15-billion, debt-financed deal.

In the wake of the financial crisis, it seemed the high-wire act might fail. But as the auto market rebounded, Continental's share price soared.

Georg and Maria-Elisabeth's combined 46% stake in Continental accounts for most of their wealth.