Django admin - property options based on a related parent model

I have a parent and a child class. The relation between them is many-to-one like this:

class Parent(AccessmanagerMixin, models.Model):
    name = models.CharField(max_length=150)
    def __str__(self) -> str:
        return self.name

class Child(AccessmanagerMixin, models.Model):
    name = models.CharField(max_length=150)
    parent_group = models.ForeignKey(Parent, on_delete=models.CASCADE,  null=True )
    def __str__(self) -> str:
        return self.name

they both have a many-to-many relation with the User class, named read_users (its a custom security on object level).

class AccessmanagerMixin(models.Model):
    read_users = models.ManyToManyField(User, related_name='read_users')
    class Meta:
        abstract = True

For example in the admin I would like to use the users from Parent read_users as an option for selecting the read_users for the Child entity? How can I do this in a best way? Can I override the read_users property in the Child admin.ModelAdmin.