Industry: Puerto Rico's Brother Act

This is the palmy time of year in Puerto Rico, when fugitives from the mainland crowd the island's modernistic concrete hotels, hoping to warm their bones and tan their hides. Virtually every dollar the tourists spend somehow turns a profit for three forceful brothers named Ferré (rhymes with beret).

Since World War II the Ferrés—José, Luis and Herman—have built a complex of seven companies into Puerto Rico's biggest private business. Today the Ferrés make 90% of the island's cement, nearly all its bottles and most of its tile and paperboard. They also fabricate...