Dead Postmasters

On a couple of my installations, I've noticed that after a few days there
are several "dead" postmasters (i.e., not associated with any running
backend).  When I do a ps -ax (RedHat 6.1, Postgresql 6.5.3) I see:

...
[postmaster]
[postmaster]
[postmaster]
[postmaster]
[postmaster]
[postmaster]
...
and several

/usr/bin/postgres ..... lines

The problem is that there are more [postmaster] lines (sometimes 4 or 5
times as many) as there are /usr/bin/postgres lines.

When I do a kill -TERM pid on all of the [postmaster] pids or restart the
postmaster, the system gets much faster.  The problem is I also cut of
"live" connections in the process.  My question is: Is there any way I can
determine which of the [postmaster] entries are associated with which
/usr/bin/postgres entries?

Thank you!

Len Morgan