You cannot - not directly, that is - allow group members to kill other users processes. A user kann only kill his own processes, only root (more exactly: any user with uid 0) is allowed to kill any process.
You could create a workaround by using sudo: create a script which checks the group memberships of originator and process in question and which kills the process accordingly. Let this script run with root authority and use sudo to authenticate its use.
It would have been a really nice gesture of friendship to tell us what this solution would be. Kind of returning the favour after asking us a question and getting an attempt to help you.
Many thanks for your contribution to the community.
The solution(which i got from scripting section)
is that I'll use a common user who will start and kill the process
so instead of calling my script that creates the process I call another script that switches (temporary) to a common user then call the script that creates the process then switch back to the original user,and the same goes when I want to kill the process. but not forgetting that the new script should be Execute Only since it contains the password of the common user.
the whole idea is to make a single common user to create and kill the process