如何使用jquery验证来自输入数组的至少一个输入

$('#register_form').validate({ 
  rules: {
    'firstname[]': {
      required: true,},'phone[]': {
      required: true,'email[]': {
      required: true,event: {
      required: true,messages: {
    'firstname[]': {
      required: "Please enter registrant name",'phone[]': {
      required: "Please enter registrant phone",'email[]': {
      required: "Please enter registrant email",event: {
      required: "Please check atleast one event",errorPlacement: function(error,element) {
    error.appendTo( element.closest("div") );
  },});

.registrant_table{width: 100%;border: 1px solid #ccc;text-align: center;}
.registrant_table tr td{Border: 1px solid #ccc;height: 42px;font-weight: bolder;}
.registrant_table input{Border: 0px !important;width: 100%;height: 42px;text-align: center;font-weight: normal;}
label.error{Color: red !important;}

<form method="post" action="" name="register_form" id="register_form">
  <div>
    <table class="registrant_table">
      <tr>
        <td>No</td>
        <td>Official Full Name</td>
        <td>Mobile Contact</td>
        <td>Email</td>
      </tr>
      <tr>
        <td>1</td>
        <td><input type="text" name="firstname[]"></td>
        <td><input type="text" name="phone[]"></td>
        <td><input type="text" name="email[]"></td>
      </tr>
      <tr>
        <td>2</td>
        <td><input type="text" name="firstname[]"></td>
        <td><input type="text" name="phone[]"></td>
        <td><input type="text" name="email[]"></td>
      </tr>
      <tr>
        <td>3</td>
        <td><input type="text" name="firstname[]"></td>
        <td><input type="text" name="phone[]"></td>
        <td><input type="text" name="email[]"></td>
      </tr>
      <tr>
        <td>4</td>
        <td><input type="text" name="firstname[]"></td>
        <td><input type="text" name="phone[]"></td>
        <td><input type="text" name="email[]"></td>
      </tr>
      <tr>
        <td>5</td>
        <td><input type="text" name="firstname[]"></td>
        <td><input type="text" name="phone[]"></td>
        <td><input type="text" name="email[]"></td>
      </tr>
    </table>
  </div>
  <br>
  <div class="col-md-4 col-sm-6 col-xs-12">
    <label>Please tick the event you are joining:</label><br>
  </div>
  <div class="col-md-8 col-sm-6 col-xs-12 checkBox_container">
    <input type="checkBox" name="event" value="26-27 April 2018,Royale Chulan DamanSara,Malaysia">&nbsp;&nbsp;&nbsp;26-27 April 2018,Malaysia<br>
    <input type="checkBox" name="event" value="3-4 May 2018,Grand Hyatt,Singapore">&nbsp;&nbsp;&nbsp;3-4 May 2018,Singapore<br>
    <input type="checkBox" name="event" value="Royal Plaza Hotel,Mongkok,Hong Kong">&nbsp;&nbsp;&nbsp;Royal Plaza Hotel,Hong Kong<br>
    <input type="checkBox" name="event" value="Grand Hyatt,Menteng,Jakarta,Indonesia">&nbsp;&nbsp;&nbsp;Grand Hyatt,Indonesia<br>
  </div>
  <p>&nbsp;</p>
  <p style="text-align: center;"><input type="submit" value="submit" name="submit"></p>
</form>

我添加了我的代码小提琴here

它适用于一个注册人.不能使用多个相同的输入.

我的问题是：

>案例1：

如何验证至少一个注册人的所有输入(姓名,电子邮件)是否已填写？
>案例2：

如果一个注册人填写了所有三个输入.然后我只填写第二个注册人的姓名(或电话或电子邮件).然后点击提交.

如何显示第二个注册人的电话和电子邮件的错误消息？

如果用户没有注册第二个注册人名称或电话或电子邮件.不需要
验证该行. (对3,4,5等其他注册人也一样).

我需要满足这两种情况.