diff --git a/accessible/aom/AccessibleNode.cpp b/accessible/aom/AccessibleNode.cpp
index dcf5afdfdcee..7fb0f05c4854 100644
--- a/accessible/aom/AccessibleNode.cpp
+++ b/accessible/aom/AccessibleNode.cpp
@@ -47,6 +47,7 @@ AccessibleNode::AccessibleNode(nsINode* aNode) :
     mIntProperties(3),
     mUIntProperties(6),
     mBooleanProperties(0),
+    mRelationProperties(3),
     mStringProperties(16),
     mDOMNode(aNode)
 {
diff --git a/accessible/aom/AccessibleNode.h b/accessible/aom/AccessibleNode.h
index 774cec0d8a27..d56981b7c866 100644
--- a/accessible/aom/AccessibleNode.h
+++ b/accessible/aom/AccessibleNode.h
@@ -51,6 +51,17 @@ struct ParentObject;
     SetProperty(AOMStringProperty::e##name, a##name);        \
   }                                                          \
 
+#define ANODE_RELATION_FUNC(name)                       \
+  already_AddRefed<AccessibleNode> Get##name()          \
+  {                                                     \
+    return GetProperty(AOMRelationProperty::e##name);   \
+  }                                                     \
+                                                        \
+  void Set##name(AccessibleNode* a##name)               \
+  {                                                     \
+    SetProperty(AOMRelationProperty::e##name, a##name); \
+  }                                                     \
+
 #define ANODE_PROPS(typeName, type, ...)                     \
   enum class AOM##typeName##Property {                       \
     MOZ_FOR_EACH(ANODE_ENUM, (), (__VA_ARGS__))              \
@@ -63,6 +74,12 @@ struct ParentObject;
   };                                                          \
   MOZ_FOR_EACH(ANODE_STRING_FUNC, (), (__VA_ARGS__))          \
 
+#define ANODE_RELATION_PROPS(...)                               \
+  enum class AOMRelationProperty {                              \
+    MOZ_FOR_EACH(ANODE_ENUM, (), (__VA_ARGS__))                 \
+  };                                                            \
+  MOZ_FOR_EACH(ANODE_RELATION_FUNC, (), (__VA_ARGS__))          \
+
 #define ANODE_ACCESSOR_MUTATOR(typeName, type, defVal)                          \
   nsDataHashtable<nsUint32HashKey, type> m##typeName##Properties;               \
                                                                                 \
@@ -164,6 +181,12 @@ public:
     ValueNow
   )
 
+  ANODE_RELATION_PROPS(
+    ActiveDescendant,
+    Details,
+    ErrorMessage
+  )
+
 protected:
   AccessibleNode(const AccessibleNode& aCopy) = delete;
   AccessibleNode& operator=(const AccessibleNode& aCopy) = delete;
@@ -213,9 +236,29 @@ protected:
   ANODE_ACCESSOR_MUTATOR(Int, int32_t, 0)
   ANODE_ACCESSOR_MUTATOR(UInt, uint32_t, 0)
 
+  already_AddRefed<AccessibleNode> GetProperty(AOMRelationProperty aProperty)
+  {
+    RefPtr<AccessibleNode> data;
+    if (mRelationProperties.Get(static_cast<int>(aProperty), &data)) {
+      return data.forget();
+    }
+    return nullptr;
+  }
+
+  void SetProperty(AOMRelationProperty aProperty,
+                   AccessibleNode* aValue)
+  {
+    if (!aValue) {
+      mRelationProperties.Remove(static_cast<int>(aProperty));
+    } else {
+      mRelationProperties.Put(static_cast<int>(aProperty), aValue);
+    }
+  }
+
   // The 2k'th bit indicates whether the k'th boolean property is used(1) or not(0)
   // and 2k+1'th bit contains the property's value(1:true, 0:false)
   uint32_t mBooleanProperties;
+  nsDataHashtable<nsUint32HashKey, RefPtr<AccessibleNode> > mRelationProperties;
   nsDataHashtable<nsUint32HashKey, nsString> mStringProperties;
 
   RefPtr<a11y::Accessible> mIntl;
diff --git a/accessible/tests/mochitest/aom/test_general.html b/accessible/tests/mochitest/aom/test_general.html
index e8a379e12f46..6ae9dc48283a 100644
--- a/accessible/tests/mochitest/aom/test_general.html
+++ b/accessible/tests/mochitest/aom/test_general.html
@@ -84,6 +84,13 @@
     is(anode[prop], null, `anode.${prop} was assigned null`);
   }
 
+  function testRelationProp(anode, node, prop) {
+    is(anode[prop], null, `anode.${prop} should be null`);
+    anode[prop] = node.accessibleNode;
+    is(anode[prop], node.accessibleNode, `anode.${prop} was assigned AccessibleNode`);
+    anode[prop] = null;
+    is(anode[prop], null, `anode.${prop} was assigned null`);
+  }
   // Check that the WebIDL is as expected.
   function checkImplementation(ifrDoc) {
     let anode = ifrDoc.accessibleNode;
@@ -188,6 +195,12 @@
     let adopted_node = anotherDoc.adoptNode(node);
     is(anode, adopted_node.accessibleNode, "adopting node to another document doesn't change node.accessibleNode");
 
+    const relationProps = ["activeDescendant", "details", "errorMessage"];
+
+    for (const relationProp of relationProps) {
+      testRelationProp(anode, node, relationProp);
+    }
+
     finish();
   }
   </script>
diff --git a/dom/webidl/AccessibleNode.webidl b/dom/webidl/AccessibleNode.webidl
index 478fe24c94dd..f121c8bad702 100644
--- a/dom/webidl/AccessibleNode.webidl
+++ b/dom/webidl/AccessibleNode.webidl
@@ -61,6 +61,11 @@ interface AccessibleNode {
   attribute DOMString? live;
   attribute DOMString? relevant;
 
+  // Other relationships
+  attribute AccessibleNode? activeDescendant;
+  attribute AccessibleNode? details;
+  attribute AccessibleNode? errorMessage;
+
   // Collections.
   attribute long? colCount;
   attribute unsigned long? colIndex;