How to send a signal to a child's child after receive a signal from parent

Question

Background: I am child (A)

Original Code:
Parent-> fork [hv A PID only]
------------1st Child(A)-> fork twice [hv Aa PID and Ab PID]
-------------------->1st Child's Child(Aa) + 2nd Child's Child(Ab)

This time, I would like to send a signal SIGCONT to child's children (Aa+Ab) after receive a signal SIGCONT from parent. What should I do?

Answer 1

create a process group and send a signal to it. See http://linux.die.net/man/2/killpg