'genericLine' is not a member of 'TInfluenceDiagram' but it is

Question

In my code, I have a file VisualForm.h/.cpp that needs access to a private member in MainWindow.h/.cpp.

My MainWindow.h includes the following (relevant) files:

#include "connLines.h"
#include "nodeShapes.h"
#include "VisualForm.h"

My MainWindow.h contains a class, TInfluenceDiagram, which has public members as listed:

class TInfluenceDiagram : public TForm
{
public:     // members
    connLine genericLine;
    int tempSaveX, tempSaveY;
}

MainWindow.cpp declares a pointer to the window that is created:

TInfluenceDiagram *InfluenceDiagram;

connLine is a class that I have defined in the connLines.h/.cpp files.

My VisualForm.h includes the following relevant files in this order:

#include "connLines.h"
#include "MainWindow.h"

And contains this struct:

struct connProperties{
    connLine conn;
    TPoint linepoints[2];
}connProperties;

In my VisualForm.cpp file is where I am getting my error. This file needs access to MainWindow's genericLine public member but my compiler is telling me that it is not a member of TInfluenceDiagram. Here is the function that produces the error:

void __fastcall TVisualPropertiesForm::Button1Click(TObject *Sender)
{
    InfluenceDiagram->tempSaveX = 0;      //This public member is accessed just fine
    InfluenceDiagram->genericLine = connProperties.conn;; //Error here
}

The exact error I get in C++ Builder XE8 is: "[bcc32 Error] VisualForm.cpp(331): E2316 'genericLine' is not a member of 'TInfluenceDiagram'"

This stackoverflow question is similar: Compiler saying variable is not a member of class when it is But I have tried changing the order of the includes as suggested in the top answer but to no avail so I have posted this as a new question. Any help would be greatly appreciated.