closing parent process(terminal) doesn't close a specific child process

I'm new to Linux and so far,I have come to understand that if we open a new process through a gnome-terminal eg: gedit & "& for running it in background", then if we close the terminal, gedit exits as well. So, to avoid this ,we disown the process from the parent terminal by giving the process id of gedit.

But, I've come across one peculiarity; If we open a gnome-terminal from within a gnome-terminal(parent) with gnome-terminal & and now, if we close the parent terminal, the child terminal doesn't close even if I haven't disowned it.

Why is it? And if there is an exception, what is the reason for making it an exception and where can I find the configuration file(if accessible) where this exception has been mentioned?