child

function travel_log_child_update_option_vals( $value, $old_value ) {
      update_option( 'theme_mods_' . get_template(), $value );
      return $old_value; // prevent update to child theme mods
 }

function travel_log_child_customizer_default_vals_update( $default ) {
     return get_option( 'theme_mods_' . get_template(), $default );
 }

function travel_log_child_customizer_parent_options_import() {

if ( get_stylesheet() !== get_template() ) {
 add_filter( 'pre_update_option_theme_mods_' . get_stylesheet(), 'travel_log_child_update_option_vals', 10, 2 );
 add_filter( 'pre_option_theme_mods_' . get_stylesheet(), 'travel_log_child_customizer_default_vals_update' );
}
}

add_action('init', 'travel_log_child_customizer_parent_options_import');