What process started/owns another process?

[Peter S Galbraith]

I have a lot of these processes on my system:

$ ps aux
[cut]
root      2717  0.0  0.0     0    0 ?        Z    11:43   0:00 [sh <defunct>]
root      2718  0.0  0.0     0    0 ?        Z    11:44   0:00 [sh <defunct>]
root      2722  0.0  0.0     0    0 ?        Z    11:45   0:00 [sh <defunct>]
root      2726  0.0  0.0     0    0 ?        Z    11:45   0:00 [sh <defunct>]
[cut]

How do I determine what process started them?

Thanks,
Peter