Using the ps command (process status),

 ps -ef | grep pm
   

you can see that pm's pid is 0 and ppid is also 0.

Similarly, the parent of other servers (vfs, vm, rs, etc) is also 0.

This is a bit of an anomaly. pm is not the parent of the other servers or itself!

Using ps, init's pid is 1 and init's ppid is 0 as it is in Unix/Linux.

But in Unix/Linux, all other processes have pid's that indicate they are descended from init (child, granchild, etc), not from pid 0.