when to use #include?

[globaltourist]

I'm currently writing a pretty big program separated into .cpp and .h file and i have a question about #include's:
-I know that if i include an existing c++ library (that is not external) twice the second one will be ignored due to the #ifndef #define and #endif preprocessor directives.
-what confuses me is should i for example include the same libraries inside the .cpp and .h files the are having a "has-a" relationship ?
example:

File_scanner.h

#ifndef File_scanner
#define File_scanner
#include<iostream>
#include<fstream>
#include<sstream>
//i spare the code or the post will be too long
#endif 

File_scanner.cpp

#include "File_scanner.h"
//should i define the same libraries as in File_scanner.h?
//i spare the code or the post will be too long 

File_compressor.h

#ifndef File_compressor
#define File_compressor
#include "File_scanner.h"
//this class has a "has a" relationship with File_scanner and use the same
//libraries.
//should i include the File_scanner.h or use the libraries in it instead/in addition to the
//#include "File_scanner.h"?  
//i spare the code or the post will be too long
#endif 

File_compressor.cpp

#include "File_compressor.h"
//should i use the libraries in addition to the File_compressor.h ?
//(same libraries as in its .h includes)
//i spare the code or the post will be too long 

[globaltourist]

yes but the question is about coding style it just doesn't seem right the way i use it although it does obviously work.

[keskiverto]

See:
https://herbsutter.com/2013/08/19/gotw-7a-solution-minimizing-compile-time-dependencies-part-1/
https://herbsutter.com/2013/12/31/gotw-7b-solution-minimizing-compile-time-dependencies-part-2/
https://herbsutter.com/2013/12/31/gotw-7c-minimizing-compile-time-dependencies-part-3/
https://herbsutter.com/gotw/_100/
https://herbsutter.com/gotw/_101/

That said, some compilers support "precompiled headers" -- a way to lessen the need to recompile non-changing set of included headers (like the Standard Library).