it is very rare for a family business to make it past the third generation
Couldn't agree more, I have seen far to many multi generational businesses fail (JCB is probably one of the bigger exceptions) to the point that my kids have no attachment to my businesses and need to make their own way in life to suit themselves. It is inevitable that this was going to happen at some point in time - Aston Martin, Bentley, Rolls Royce and Lotus have survived the transition from family ownership. Fingers crossed that it works out well for them.
