Johanna Quandt and children Suzanne and Stephan own 50% of BMW , makers of the ultimate driving machine. Last year, sales of BMW cars rose 19% to boost BMW Group sales to a record $31 billion. The Quandt family fortunes rose accordingly, by nearly $5 billion to $17.5 billion. These days, it seems BMWs are as ubiquitous as Toyotas. Still, the family is determined to keep the company independent.