'Helper function to extend the form
@param person: the person (Row)
@param formfields: list of form fields (Field)
@param data: the form data (dict)
@param hidden: hidden form fields (dict)
@param permitted: whether the action is permitted
@return: tuple (widget_id, submit_label)'

def get_form_data(self, person, formfields, data, hidden, permitted=False):

    T = current.T
    if person:
        details = dvr_get_household_size(person.id, dob=person.date_of_birth)
    else:
        details = ''
    formfields.extend([Field('details', label=T('Family'), writable=False)])
    data['details'] = details
    widget_id = 'case-event-form'
    submit = current.T('Register')
    return (widget_id, submit)
