I need some insight about classes design

I have the GUI file called ui_smbhelper.py

class Ui_SMBWindow(object):
    def setupUi(self, SMBWindow):
        if not SMBWindow.objectName():
            SMBWindow.setObjectName(u"SMBWindow")
        SMBWindow.resize(852, 486)
        self.actionQuit = QAction(SMBWindow)
        self.actionQuit.setObjectName(u"actionQuit")
        self.actionAbout = QAction(SMBWindow)
        self.actionAbout.setObjectName(u"actionAbout")
        self.centralwidget = QWidget(SMBWindow)
#More code here

This is obtained with piuic6. It is the GUI of the project.
This is smbhelper_functions.py

class SmbHelper(QMainWindow, Ui_SMBWindow):
    def __init__(self, app):
        super().__init__()
        self.setupUi(self)
        self.app = app
        # Variables
        self.samba_ip = self.line_samba_ip.text()
        self.samba_share = self.line_samba_share.text()
        self.samba_user = self.line_samba_user.text()
        # More imports
        # SLOTS
        self.button_apply.clicked.connect(self.apply_clicked)
        self.button_cancel.clicked.connect(self.close_clicked)
        self.actionQuit.triggered.connect(self.close_clicked)

I want it to work as a sort of controller for other 2 classes I have: FstabConfig and SambaConfig

class SambaConfig:
    def __init__(self, smb_helper):
        # Folder creation
        def check_credentials_folder(self):
# more methods here

class FstabConfig(SmbHelper):
    def fstab_create_temp(self):
        fstab_tmp = self.fstab_read()      


# more methods here

The problem is those are sons of SmbHelper, but, I need that functions to be called in SmbHelper, but it’s not good to instantiate sons on father, but I can’t break inheritance because I need the variables in order the functions in SambaConfig and FstabConfig work, and I am in a catch 22 here.
How can I design my classes: hierarchy and relationships?