When a site is removed from a site group, it no longer will share 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.
Select the site group to edit
Click the + icon from the Actions menu and select Edit.
The Site Group panel appears.
Click the Sites in Group property and then click the Remove Site icon in the Sites in Group panel. The site will be removed from the site group.
Click Save to save the site group.