C++ :: Automatically Attaching Objects To Parent Class

In my program, I create controls by deriving base objects of them I've made. These controls are then are attached within the OnCreate() function via a method I've created. For example:

Code:
class tChat: public TextBox {
public:
void OnKeyDown(UINT &KeyCode) {
if (KeyCode == VK_RETURN) {
MessageBox(NULL, "Pressed enter!", NULL, 0);
[Code] ....

The use of AddControl() feels quite redundant and is only their to parse a pointer to txtChat's Parent. I'm trying to see if it's possible to remove this line and automatically associate txtChat to fMain.

Currently my hierarchy looks like:

[User's derived Form] -> [MDIForm or Form] -> [FormBase] -> [Object]
[User's derived Control] -> [TextBox, etc..] -> [Control] -> [Object]

The user can then derive the Form and Controls and use their virtual OnEVENT functions to handle all the messages they expose.

So far my first concept is using the order-of-creation based on base-class constructor's being fired to determine which object is associated with what.

If I create a copy of a class (i.e. a Form-derived object), first the Form's constructor is fired, and then the constructor's of any class-based member-variables are fired. Is this a safe assumption? I imagine the only time this could be affected is by another thread creating the object of a Form or Control derivative?

If this assumption is true, I could save the 'this' pointer from the FormBase constructor, and then associate it with each Control via the base Control class' constructor? Then to ensure thread-safety, I could map the current FormBase pointer to the local thread id to ensure no conflict if multiply threads are creating forms at the same time?

I've created some mock-up code before trying to implement this into my main code. The following keeps track of the current Form being created by using a ThreadId-based map. When a control is created it gets the FormBase pointer based of it's ThreadId calling. The control then calls an Attach() function of it's parent Form using the pointer it just got, and parses a pointer to the control. The Form then adds the control's pointer to a list. When the Form eventually parses WM_CREATE, it automatically pulls the controls from the list and fires their virtual Create() functions to build them.

Mock-up:

Code:
#include <Windows.h>
#include <string>
#include <map>
#include <list>
class FormBase;// Forward declaration
class FormMap;// Forward declaration
class Object {};// Base Object

[Code] ....

Is this plausible to use? I imagine C++ does not have many "guarantees" about how it creates objects and when. But I thought it would be safe that it would never create member-variables before the class of them is first created?