C++ ::  How To Create Umbrella Type

Any way to create an "umbrella" type/class/struct of existing c++ types or windows types.

I want to address ~3 different structs with a single pointer and downcast but, they are not a part of the same hierarchy.

Is there a way that I could for example's sake, include a POINT and a RECT under some "umbrella" type so I can go like this:

// Working Variables
//---------------------------------------------------------
Umbrella* pUmbType1(NULL);
Umbrella* pUmbType2(NULL);
POINT ptExamp = { 0 };
RECT egRect = { 0, 0, 0, 0 };

// Typecast POINT and RECT to umbrella pointer
//---------------------------------------------------------
pUmbType1 = (Umbrella*)ptExamp;
pUmbType2 = (Umbrella*)egRect;

I want to do this, so I don't have to duplicate code for each type.