I Don't Want to Appraise an Employee Who is in Performance Pro

I have two family members who work with me whom I am the supervisor of but I don't want to appraise them. Is there a setting I can select to turn appraisals off for them? I still want them in the system as they are appraisers of other employees?

No, there is not a setting to turn off appraisals for individual employees.  

However, the cycle dates can be changed to a date well in the future to avoid any reminders or notices being sent to them or their supervisors regarding an upcoming or overdue appraisal.