I'm trying to evaluate process' state between two "sibling" processes (processes created by the same parent process); using the .is_alive() and exitcode to evaluate whether a process has been init'd, started, finished successfully or unsuccessfully. 
The reference to one process is passed to the other and I'd like to call .is_alive(). This raises the following assertion error:

Process C-2:
Traceback (most recent call last):
  File "/usr/lib/python3.7/multiprocessing/process.py", line 297, in _bootstrap
    self.run()
  File "/home/timms/.PyCharm2019.2/config/scratches/is_alive_method.py", line 59, in run
    print("brother - ",self.brother.state)
  File "/home/timms/.PyCharm2019.2/config/scratches/is_alive_method.py", line 16, in state
    if self.is_alive():
  File "/usr/lib/python3.7/multiprocessing/process.py", line 151, in is_alive
    assert self._parent_pid == os.getpid(), 'can only test a child process'
AssertionError: can only test a child process

It's obvious that the assertion fails given the family structure of the processes. Overwriting the is_alive() method in my own process class appears to produce my desired output behaviour - with assertion and discarding self removed (see attachment).

Is there something fundamental to how process' operate that I should be weary of? I understand that is_alive also joins itself if possible; is that the sole reason for the assertion? Could a method that mirrors is_alive() without the assertion and discard method work with the desired intention I've described above?