While forks of private repositories are deleted when a collaborator is removed, the person will still retain any local clones of your repository.
- On GitHub.com, navigate to the main page of the repository.
- Under your repository name, click Settings. If you cannot see the "Settings" tab, select the dropdown menu, then click Settings.
- In the "Access" section of the sidebar, click Collaborators & teams.
- To the right of the collaborator you want to remove, click Remove.