$pro = array(
          'one' => get_post_meta( $id, $key.'one', true )?get_post_meta( $id, $key.'one', true ):'',

);
<label for="one" class="checkbox">
    <input type="checkbox" name="one" value="<?php echo $pro['one']; ?>" />
    <?php _e( 'TEXT', 'theme' ); ?>
</label>