Creating a child gameObject from a parent script while running (aka not using eg. start() or Selection)

Hello... First question:

I'd like to have a parent "TreeCreator" class declare, initialize, and spawn a new child gameObject, "Heart" with the component heart.cs (I saw the addComponent thing so that shouldn't be a problem).

Here's what I have so far (from another example):

 [MenuItem("GameObject/Create Empty Child #&c")]
     // Use Shift+Alt+c
     // For initialization
     static void createEmptyChild () {
         GameObject heart = new GameObject("Heart");
         Instantiate (heart,     
             Vector3(Transform.position.x, Transform.position.y, Transform.position.z),
             Quaternion.identity);
         heart.transform.parent = tree.activeTransform.parent;
         heart.transform.Translate(Selection.activeTransform.position);
     }

I get an error for tree.activeTransform.parent //UnityEngine.GameObject doesn't contain this I understand from another tutorial that if I did "Selection.activeTransform.parent" it would work but I don't want to have to select each object that I want to create a child in because I will be generating thousands of these "TreeGeneration" gameObjects all with their own "Heart" class.

Any help or push in the right direction is greatly appreciated.