When a site is removed from a site group, it no longer shares the site group shareables until added to another group containing the shareables.
Open the Business Control Center.
Select Site Administration.
Select the Site Assets link.
Enter the name of a project and click Continue.
Right-click the site group to edit, and click Edit. The Site Group panel appears.
Right-click the sites in the site group you want to remove, and click Delete.
Click Save to save the site group.