Getting duplicate data in database table 'family'

I am having an issue with duplicate data being inserted into my database table called 'family'. Here's the relevant code:

HTML Form:

  <form action="{{url('requestFormData')}}" id="multi-step-form" class="multi-step-form" method="POST">
                                    <div>
                                           
                                             @csrf
                                         <section class ="form-section">
                                         <h4>Client Info</h4>
                                            <div class="row">
                                                <div class="col-lg-2 mb-4">
                                                    <div class="form-group">
                                                        <label class="text-label">First Name*</label>
                                                        <input type="text" name="firstName" class="form-control" placeholder="FirstName" required>
                                                    </div>
                                                </div>
                                                <div class="col-lg-2 mb-4">
                                                    <div class="form-group">
                                                        <label class="text-label">Last Name*</label>
                                                        <input type="text" name="lastName" class="form-control" placeholder="LastName" required>
                                                    </div>
                                                </div>
                                              
                            
                                                  <div class="card-body col-lg-2 mb-4">
                                                    <div class="form-group">
                                                  <p class="mb-0">Referal date</p>
                                                   <input name="datepicker" class="datepicker-default form-control" id="datepicker">
                                                  </div>
                                                   </div>

                                                 
                                                   <div class="card-body col-lg-2 mb-4">
                                                    <div class="form-group">
                                                  <p class="mb-0">Contact date</p>
                                                   <input name="datepicker" class="datepicker-default form-control" id="datepicker">
                                                  </div>
                                                   </div>
                                               
                                                
                                                 
                                                  
                                                   <div class="col-lg-5 mb-4">
                                                    <div class="form-group">
                                                        <label class="text-label">Phone Number*</label>
                                                        <input type="text" name="phone_number" class="form-control" placeholder="Phone Number" required>
                                                    </div>
                                                </div>


                                                <div class="col-lg-5 mb-4">
                                                    <div class="form-group">
                                                        <label class="text-label">Move in date*</label>
                                                        <input type="text" name="moveindate" class="form-control" placeholder="Move In Date" required>
                                                    </div>
                                                </div>




                                                <div class="col-lg-12 mb-4">
                                                    <div class="form-group">
                                                        <label class="text-label"> Address</label>
                                                        <div class="input-group">
                                                            <input type="text" class="form-control"  name="address" id="inputGroupPrepend2" aria-describedby="inputGroupPrepend2" placeholder="address 1" required>
                                                        </div>
                                                    </div>
                                                </div>
                                               

                                                <div class="col-lg-1 mb-4">
                                                    <div class="form-group">
                                                        <label class="text-label">Number of Adults *</label>
                                                        <input type="number" name="numberofAdults" id = "numberofAdults" min ="0"  max ="10" class="form-control" onchange="addAdultFields()" required>
                                                    </div>
                                                </div>

                                                <div class="col-lg-1 mb-4">
                                                    <div class="form-group">
                                                        <label class="text-label">Number of Children*</label>
                                                        <input type="number" name="numberofChildren" id = "numberofChildren" min ="0" max ="10" class="form-control" onchange="addChildrenFields()" >
                                                    </div>
                                                </div>

                            
                                               
                                      </section>

  
                                <button type="button" class ="  previous btn btn-primary float-left"> previous </button>
                                
                                <button type="button" class =" next btn btn-primary float-right">Next  </button>

                                <button type="submit" class =" btn btn-success float-right"> Submit </button>

                                </div>
here is my php code which submits to the database

  public function postdata(Request $req){


   // handeling first serction of multi step form 
         $firstname = $req ->input('firstName'); // taking data from the firstname text field on the request form 
         $lastname  = $req ->input('lastName'); // taking data form the lastname text field on the request form
         $phone_num = $req ->input('phone_number'); // ||
         $address   = $req ->input('address'); // ||
         $numAdults = $req ->input('numberofAdults'); //||
         $numkids   = $req ->input('numberofChildren');
        $data = array('headofhousehold_firstname' => $firstname, "headofhousehold_lastname" => $lastname, "phone" => $phone_num, "address" => $address, "numofadults" => $numAdults, "numofkids" => $numkids);
       

        
        DB::table('family') -> insertOrIgnore($data);
       
 
here is my route

 Route::get('postdata','RequestInsertController@insform'); // this route is used to display the form view when /postdata is accessed 

   
Route::post('requestFormData',[RequestInsertController::class, 'postdata'])->name('postdata');
when I click the submit it work but i get a duplicate with each user but they have a different family id. example I add a user John Doe I get it twice with a different ID when I wanted one. I also tried making phone a unique key but I get a different error. here is the error message after setting phone as unique SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '1234567890' for key 'phone'

here is the family table
<pre lang="SQL">CREATE TABLE IF NOT EXISTS `family` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `headofhousehold_firstname` varchar(20) NOT NULL,
  `headofhousehold_lastname` varchar(20) NOT NULL,
  `phone` varchar(15) NOT NULL,
  `address` text NOT NULL,
  `numofadults` int(11) NOT NULL,
  `numofkids` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ;

I've tried making the 'phone' field a unique key, but I get a different error. How can I prevent duplicate data from being inserted into the 'family' table while still allowing multiple entries for the same firstname , lastname ? Any help would be appreciated.