MB User Profile -> Registration form -> inherit field values

Hi,

I have a user registration form which asks for first_name and last_name which corresponds to the WP first/lastname.

In addition, user has to enter one or more children and their names. I would like the last name of each children to "inherit" the entered last_name.

Is that possible at all?

Thanks

Martin

add_filter( 'rwmb_meta_boxes', 'your_prefix_register_meta_boxes' );

function your_prefix_register_meta_boxes( $meta_boxes ) {
    $prefix = '';

    $meta_boxes[] = array (
        'id' => 'dsk-user-registration',
        'fields' => array(
            array (
                'id' => $prefix . 'first_name',
                'type' => 'text',
                'name' => esc_html__( 'First Name', 'text-domain' ),
            ),
            array (
                'id' => $prefix . 'last_name',
                'type' => 'text',
                'name' => esc_html__( 'Last Name', 'text-domain' ),
            ),
            array (
                'id' => $prefix . 'dsk_user_registration_mobile_number',
                'type' => 'text',
                'name' => esc_html__( 'Mobile Number', 'text-domain' ),
                'required' => 1,
            ),
            array (
                'id' => $prefix . 'dsk_user_registration_group_child',
                'type' => 'group',
                'name' => esc_html__( 'Child(ren)', 'text-domain' ),
                'fields' => array(
                    array (
                        'id' => $prefix . 'dsk_user_registration_group_child_firstname',
                        'type' => 'text',
                        'name' => esc_html__( 'First Name', 'text-domain' ),
                        'required' => 1,
                    ),
                    array (
                        'id' => $prefix . 'dsk_user_registration_group_child_lastname',
                        'type' => 'text',
                        'name' => esc_html__( 'Last Name', 'text-domain' ),
                        'required' => 1,
                    ),
                    array (
                        'id' => $prefix . 'dsk_user_registration_group_child_legal_guardian_type',
                        'name' => esc_html__( 'Your relationship', 'text-domain' ),
                        'type' => 'radio',
                        'options' => array(
                            'Father' => esc_html__( 'Father', 'text-domain' ),
                            'Mother' => esc_html__( 'Mother', 'text-domain' ),
                            'Other' => esc_html__( 'Other', 'text-domain' ),
                        ),
                        'inline' => 1,
                        'required' => 1,
                    ),
                ),
                'clone' => 1,
                'default_state' => 'expanded',
                'add_button' => esc_html__( 'Add additional child', 'text-domain' ),
            ),
        ),
        'type' => 'user',
    );

    return $meta_boxes;
}