You can use the Object > Group/Member & Related Objects window to record the relationships between object records. You can record relationships of objects where they are of the same "level" and you can also record hierarchical relationships between records.
If you are recording relationships between records without a hierarchy, you can use the Related Objects table at the bottom of the Object > Group/Member & Related Objects window.
If you are recording hierarchical relationships between records for archival material, see the page on Archives.
You can also use this for other hierarchically related materials. Such as a photo album full of photographs.
If you are recording hierarchical relationships between records it is useful if every record has the Level of Current Object Record field filled in. If the terms you need don't already exist, you can create them: Creating Authority Terms.
Once you have added the Level of current Object Record, you can link the sub-records to the parent record. Go to each of the sub-records, and add the record that sits above the one you have open in the Next Higher Record in Group field.
Changing the location of the group object record does not automatically update the locations of any member object records.
The records in a group can be moved together by using the Bulk Move tool.