title: Django models count children and grand children
body: <p>In Django models I need help selecting count of children and count of grand children.
  My models:</p>
  
  <pre><code>Parent:
  
  Child:
   parent = models.Foreignkey(Parent)
  GrandChild:
   child = models.Foreignkey(Child)
  </code></pre>
  
  <p>I did </p>
  
  <pre><code>Parent.objects.annotate(num_child =Count('child’), num_grandchild=Count('child__grandchild'))
  </code></pre>
  
  <p>With this, I get num_child is exactly same value as num_grandchild</p>
  
  <p>Can you please help</p>