I can see that you are handling a mixed workforce, and this can present some conflict of interest, especially in cases relating to friends and family. But all the same, you may need to bite the bullet and show someone the door. To do that, take heed of the following two points:
Understand and communicate the reason effectively
There are many reasons for firing an employee and hence each reason will determine the kind of approach to be taken. For instance, if it is necessitated by circumstances beyond your control and that of your employee, you have to approach it in a very compassionate manner. For instance, if the company can no longer afford to pay the employee, you need to make it known to them clearly and sympathetically.
If on the other hand it is the employee’s fault such as incompetence or even criminal activities, then your approach shall be different. You will need a military approach to kick out an insubordinate or stealing employee.
Exhaust all the avenues
You should always remember that firing an employee (unless for criminal reasons and insolvency) should be the last resort. If it is a matter of minor indiscipline or incompetence, try all the possible ways to help them reform and warn them formally in writing. Only when all this fails should you go ahead and fire them.