Ember nested route not work properly

i am very new to Ember I have a template which has the list of categories. When i click on a link in the list a nested template is correctly showing. When i click another category the URL correctly changes but nested template not updated My router:

Router.map(function() {

  this.route('subcategory', { path: "/:sub_id"}, function() {
    this.route('items', { path: "/:item_id"  })
  });

});

Parent template:

<div class="todo">
            <ul class="todo-list">
              
              <li>

                <span class="desc"></span>
    <span class="label label-info" >    <i class="fa fa-barcode" ></i> </span>


              </li>
              

            </ul>
          </div>

What am I doing wrong? Thanks !