Family Employee

Our estimates indicate that being a family employee instead of a regular employee in the private sector significantly reduces both the probability and duration of absence to a substantial degree.

The evidence is from the European Community and the paper is by Block et al. They explain:

Our results are also consistent with the view that family employees have a more pronounced interest in the profitability of the business they work in, relative to regular private sector workers, because the may eventually inherit the firm. 

A draft (2014) is here. 
But there is also the Fredo Factor.