Removed the "parent" agg

404_Parent_Child.asciidoc

@@ -6,7 +6,7 @@ include::404_Parent_Child/50_Has_child.asciidoc[]
 
 include::404_Parent_Child/55_Has_parent.asciidoc[]
 
-include::404_Parent_Child/60_Parent_child_aggs.asciidoc[]
+include::404_Parent_Child/60_Children_agg.asciidoc[]
 
 include::404_Parent_Child/65_Grandparents.asciidoc[]
 

404_Parent_Child/60_Children_agg.asciidoc

@@ -0,0 +1,46 @@
+[[children-agg]]
+=== Children aggregation
+
+coming[1.4.0]
+
+Parent-child supports a
+{ref}search-aggregations-bucket-children-aggregation.html[`children`
+aggregation]  as a direct analog to the `nested` aggregation discussed in
+<<nested-aggregation>>.  A parent aggregation (the equivalent of
+`reverse_nested`) is not supported.
+
+This example demonstrates how we could determine the favourite hobbies of our
+employees by country:
+
+[source,json]
+-------------------------
+GET /company/branch/_search?search_type=count
+{
+  "aggs": {
+    "country": {
+      "terms": { <1>
+        "field": "country"
+      },
+      "aggs": {
+        "employees": {
+          "children": { <2>
+            "type": "employee"
+          },
+          "aggs": {
+            "hobby": {
+              "terms": { <3>
+                "field": "hobby"
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+}
+-------------------------
+<1> The `country` field in the `branch` documents.
+<2> The `children` aggregation joins the parent documents with
+    their associated children of type `employee`.
+<3> The `hobby` field from the `employee` child documents.
+