Try this:
$(".parent_class .child_class").click(function(e) {
e.stopPropagation();
});
It prevents the event from bubbling up the DOM tree, preventing any parent handlers from being notfied of the event.
Read more about it here.
You could also use(but I haven't tried) e.preventDefault();
If this method is called, the default action of the event will not be triggered.