When a shareable is removed from a site group, none of the sites within the group will share the shareable.
Open the Business Control Center.
Select Site Administration.
Select the Manage Site Assets link.
Enter the name of a project and click Continue.
Select the site group to edit.
Click the + button from the Actions menu and select Edit.
The Site Group panel appears.
Uncheck the shared data that you no longer want to be available to all sites within the site group.
Click Save to save the site group.