If you remove a person’s access to a private repository, any of their forks of that private repository are deleted. Local clones of the private repository are retained. If a team's access to a private repository is revoked or a team with access to a private repository is deleted, and team members do not have access to the repository through another team, private forks of the repository will be deleted.
You are responsible for ensuring that people who have lost access to a repository delete any confidential information or intellectual property.
People with admin permissions to a private or internal repository can disallow forking of that repository, and organization owners can disallow forking of any private or internal repository in an organization. For more information, see "Managing the forking policy for your organization" and "Managing the forking policy for your repository."
Deleting a private repository
When you delete a private repository, all of its private forks are also deleted.
Private forks and permissions
Private forks inherit the permissions structure of the upstream repository. This helps owners of private repositories maintain control over their code. For example, if the upstream repository is private and gives read/write access to a team, then the same team will have read/write access to any forks of the private upstream repository. Only team permissions (not individual permissions) are inherited by private forks.
Changing the visibility of an internal repository
If the policy for your enterprise permits forking, any fork of an internal repository will be private. If you change the visibility of an internal repository, any fork owned by an organization or personal account will remain private.
Deleting the internal repository
If you change the visibility of an internal repository and then delete the repository, the forks will continue to exist in a separate network.