Clayton Zekelman

Clayton Zekelman owns a stake in his family's steel business, Zekelman Industries.

The $3.3 billion (revenues) company is one of North America's largest steel pipe and tube makers.

The company has also pumped more than $1 billion into Z Modular, a division that is developing modular apartment complexes in places such as Texas, Arizona and Canada.

Clayton and his brothers, fellow billionaires Barry Zekelman and Alan Zekelman, split 100% ownership of Zekelman Industries.

They sold the company to the Carlyle Group in 2006 for some $1.2 billion, but bought the business back in 2011.