Forking twice avoids zombie

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main()
{
    int pid;
    pid = fork();

    if (pid == 0) {
        // First child
        pid = fork();
        if (pid == 0) {
            // Second child
            sleep(1);
            printf("Second child: My parent PID is %d\n", getppid());
        }
    }
    else {
        // Parent process
        wait(NULL);
        sleep(2);
        system("ps -o pid,ppid,state,tty,command");
    }
    return 0;
}