Ciclic dependency problem

main_window.h

//File main_window.h --------------------
#pragma once

#include "window.h"

struct main_window {
	void close_child();
private:	
	window child;	
};

//File window.h -------------------------
#pragma once

#include <string>
#include "main_window.h"

struct window {
	window(main_window &parent) : _parent(parent) { }
	void close();
private:
	main_window &_parent;
};