Child records are not shared when Parent record is shared in CloudKit

I have an app where I can share records with other users, everything works when I share a single record, my issue is when I share a record (parent record) which has children records referencing it, I can see the parent record in the Shared Database in the CloudKit Dashboard after the user accepts the share but I don't see any of the related child records.

Based on the WWDC videos and some other threads I read, the child records are automatically shared when you share the parent record, but it's not what I'm seeing, again, I can see the parent record in the Shared Database but no child records.

Here is an overview of how the app is set up in the CloudKit Dashboard.

In the CloudKit Dashboard, I have a `Lists` and an `Items` record type, where the `Lists` record is the parent of one or many `Items`. In the `Items` schema, I have a `Reference` field type which keeps a reference to its parent list.

### Here is the code I'm using to save the parent record.

    func shareList(){       
        let share = CKShare(rootRecord: self.list)


        if let listName = self.list.object(forKey: "name") as? String {
            self.listName = self.list.object(forKey: "name") as? String
            share[CKShare.SystemFieldKey.title] = "Sharing \(listName)" as CKRecordValue?


        } else {
            share[CKShare.SystemFieldKey.title] = "" as CKRecordValue?
        }
        share[CKShare.SystemFieldKey.shareType] = "com.mySite.lists" as CKRecordValue
       
        let sharingViewController = UICloudSharingController(preparationHandler: {(UICloudSharingController, handler: @escaping (CKShare?, CKContainer?, Error?) -> Void) in
            let modRecordsList = CKModifyRecordsOperation(recordsToSave: [self.list, share], recordIDsToDelete: nil)
           
            modRecordsList.modifyRecordsCompletionBlock = {
                (record, recordID, error) in


                handler(share, CKContainer.default(), error)
            }
            CKContainer.default().privateCloudDatabase.add(modRecordsList)
        })


         sharingViewController.delegate = self
         sharingViewController.availablePermissions = [.allowPrivate]
         self.navigationController?.present(sharingViewController, animated:true, completion:nil)
    }

What I'm I missing? Is there any additional set up I need to do when sharing the parent record?

I'm right saying that the child records should automatically be shared alone with the parent record?

Here is a picture that demonstrates the relationship between the items and the list is working in the `Private Database`.

https://i.stack.imgur.com/u7J3h.png