service manager and counterman related big problem

ok my service counterman is related to the service manager who has been here for 30 years. now how can i motivate this employee to do what i need him to do? Everytime I ask for something or complain i get told "its only a job".. Firing this person is out of the question. So i need advice. The owners love him and love the service manager... but i have to get him on board with the program...