Django ModelForm inheritance, subclassing and passing in an instance

I have an address model:

class Address(models.Model):
  line1 = models.CharField(max_length=100)
  ....

and an AddressForm:

class AddressForm(forms.ModelForm):
  class Meta:
    model = Address

Several models will have an address field, so instead of copy+pasting all of the fields from the AddressForm, I wanted to extend the AddressForm so I can reuse it. Specifically, I want to avoid copying+pasting all of the form fields into other app's forms and have only one AddressForm.is_valid() function.

For example, an Order will have an Address, so my plan was to do something like this:

class Order:
  address = models.ForeignKey(Address, on_delete=models.CASCADE)

class OrderForm(AddressForm):
  class Meta:
    model = Order

However, when I pass an instance to the OrderForm from the order/views.py, I'm passing instance of an Order and all of the AddressForm fields show up as blank:

form = OrderForm(instance=order)

How do I initialize the AddressForm fields from the order.address field?

I had tried this:

class OrderForm(AddressForm):
    def __init__(self, *args, **kwargs):
        kwargs['instance'] = kwargs['instance'].address
        super(OrderForm, self).__init__(*args, **kwargs)

But it doesn't work.

Is there a way to do this? Or a better way of reusing the AddressForm? Or would this only work if Order was a subclass of Address?

Cheers,