And he was a stockboy at the business when it was being built from $0 to $X million.
How is that any different than Paul Graham taking support calls at ViaWeb or Joel Spolsky putting up blinds at Fog Creek? In a family business, everyone does what it takes to make it successful. They are not inheriting the business. It is their business even if they are not listed as co-founders in the legal papers.
Those people that inherit their parents business, may have worked their ass off since they were young, but they start off ahead off the curve, simply due to the ground work laid down by their parents.