.

Engine/src/Scene/Hierarchy.cs

@@ -32,7 +32,7 @@ public class Hierarchy<T>
     {
       if (_parentLookup.ContainsKey(parObj))
       {
-        throw new ArgumentException("Object is already added to hierarchy");
+        return;
       }
 
       _childrenLookup.Add(parObj, new List<T>());