#include B.h
class A
{
    B* b
}

#include A.h
class B
{
    A* getA();
}

class A; //in B.h
class B; //in A.h

// a.h
class B; // This file needs to know that B is a class and that's all it needs
         // to know. Think of this declaration as "previews of coming
         // attractions", like at the movies.

class A
{
  // other stuff for class A members

    B* pB;

  // other stuff
};

// b.h
class A; // This file needs to know that A is a class and that's all it needs
         // to know. Think of this declaration as "previews of coming
         // attractions", like at the movies.

class B
{

  // other stuff for class B members

    A* getA();

  // other stuff
};

//main.cpp

#include <iostream>

#include "a.h"
#include "b.h"

using std::cout;
using std::endl;

int main()
{

    // create objects from Class A and Class B
    // etc.

    cout << "Included both" << endl;
    return 0;
}