To display the ancestors and children of process 12312,
including children of process 0, enter:

   proctree -a 12312

The output of this command might look like this:
1    /etc/init
   4954    /usr/sbin/srcmstr
      7224    /usr/sbin/inetd
         5958    telnetd -a
            13212    -sh
               14724    ./proctree -a 13212