Here's another piece of advice that applies to nearly every question asked here:

Break your program down into the smallest possible chunk that shows the behavior you are interested in.

In this case, I'd recommend making a script that just prints out "I'm the parent" and "I'm the child". Make them loop while saying that with different sleep values in the loops and get to where you can predict what will happen. Try forking inside a loop.

--Pileofrogs