In developed countries there is evidence of that. At least from 2002 to 2010, if we compare two stock indices, the Credit Suisse family business index, which contains companies managed by their relatives, and the MSCI (Morgan Stanley Capital Investment) world price index, which is a benchmark overall, we see that the first index performance is clearly superior to the second.
Include the source of this information: http://holtindex.credit-suisse.com/html/CSFAM_chart.html