Controller:
-------------
public cla3ss GCReps {
public GCReps(ApexPages.StandardController controller) {
}
    
  
  
    public Map<String,contactosListWrapper> getContactsByTierLevel(){
      List<Account> accresult = [SELECT id FROM account ];  
      List<Contact> result = [SELECT Account.Tier_Level__r.Name, Account.name, Name, Email FROM Contact where GC_Rep__c=true order by account.tier_level__r.Name,account.name,lastname,firstname ];
    
      // Group Contacts by Account                                
      Map<String,contactosListWrapper> contactsByTierLevel = new Map<String,contactosListWrapper>();
      for(Contact cont: result){
        if(null == cont.Account.Tier_Level__r.Name) continue;
        contactosListWrapper empresa = contactsByTierLevel.get(cont.Account.Tier_Level__r.name);
        if(null == empresa){
            contactsByTierLevel.put(cont.Account.Tier_Level__r.name, new contactosListWrapper(new List<contact>()) );    
        }
        contactsByTierLevel.get(cont.Account.Tier_Level__r.name).contactList.add(cont);
      }
      
      return contactsByTierLevel;
    }
    
    
    
    
     // List of contacts and details  
   public class contactosListWrapper {
       
       public List<Contact> contactList {get; set;}
       
       public Integer numOfContacts {
          get{
            return contactList.size();
          }
          set;
       }
       
       public Id firstOfList{
          get{
            return contactList[0].Id;
          }
          set;
       }
             
       public contactosListWrapper(List<contact> listContacts){
           contactList = listContacts;}
}

           
}

VisualForce

<apex:page showHeader="false" standardStylesheets="true" standardController="contact" extensions="GCReps" sidebar="false" docType="html-5.0" applyBodyTag="False" applyHtmlTag="False">
 <style type="text/css">
        body {
    background-color: white;
}
        .pbTitle {
        white-space:nowrap;
        border:white;
    }
     table {
     border-collapse:  collapse;
     border: 1px solid gray;
     }
     
     td {
     vertical-align:  top;
     }


    </style>
      <table border="1" cellspacing="0" width="60%" id="tbl">
    <thead>
        <th> Tier </th>
        <th> Title </th>
        <th> Name </th>
        <th> Email </th>
    </thead>
              <apex:repeat value="{!contactsByTierLevel}" var="key" >      
      <apex:repeat value="{!contactsByTierLevel[key].contactList}" var="keyvalue" > 
          <tr>
                         <td vertical-align="top" rowspan="{!contactsByTierLevel[key].numOfContacts}" 
                             style="display:{!IF(CASESAFEID(keyvalue.id)==CASESAFEID(contactsByTierLevel[key].firstOfList), 'table-data','none' )};"> 
                             {!keyvalue.Account.Tier_Level__r.name} </td>
               <td> {!keyvalue.Account.Name} </td>
          <td> {!keyvalue.Name} </td>
          <td> {!keyvalue.Email} </td>  

          </tr>
                  </apex:repeat>
          </apex:repeat>
    </table>  
</apex:page>

Test Class

@isTest

private class TestGCReps {
    static testMethod void TestGCReps() {
        
     
        PageReference pageRef = Page.GCReps;
        
        //Create test account
        Account acc = new Account(Name='Your Account Name', 
                                  recruitment_begin_date__c= Date.valueOf('2008-01-01'),
                                 AccountSource='Website',
                                  tier_level__c='a0D6A000000SzO2',
                                 recruitment_primary_contact__c='0056A000000zP7Z',
                                 billingstate='North Carolina',
                                 priority__c='High');
        
        insert acc;
         Account acc2 = new Account(Name='Cincinnati', 
                                  recruitment_begin_date__c= Date.valueOf('2008-01-01'),
                                 AccountSource='Website',
                                  tier_level__c='a0D6A000000SzO2',
                                 recruitment_primary_contact__c='0056A000000zP7Z',
                                 billingstate='North Carolina',
                                 priority__c='High');
        
        insert acc2;
        
        //Create test contact
        Contact cont = new Contact(firstname='Your first Name', 
                                   Title='Admin2', lastName = 'Your last Name', AccountID=acc.id, GC_Rep__c=true);//if you have more contact field please put in here
        insert cont;
        
        Contact cont2 = new Contact(firstname='Smithy', title='Admin', lastName = 'Johnny', Accountid=acc2.id, GC_Rep__c=true);//if you have more contact field please put in here
        insert cont2;
        
        
        system.Test.startTest();
            integer count;
       
            ApexPages.StandardController sc = new ApexPages.StandardController(acc);
            GCReps testIPF = new GCReps(sc);
            
            testIPF.getContactsByTierLevel();
        List<Contact> testContactList = new List<Contact>();
        contactosListWrapper wr = new contactosListWrapper();
        // count = TestIPF.contactosListWrapper();
           

            
        System.Test.stopTest();
    }
}