JQuery :: Checking Every Checkbox In DIV

The page I am working on will have a series of checkboxes. The boxes will be in the format of "parent" with one checkbox and then a "child" div with multiple checkboxes. The idea is being able to check a parent checkbox and have all the checkboxes in the preceding child div get checked as well.

Here is the layout:
<div class= "parent_div">
<label>
parent
</label><input type='checkbox'/>
</div>
<div class = "child_div" >
<label> child </label>
<input type = 'checkbox'/> .....
This does not work. The checkboxes do not get checked.

I know that the selector is working because if I assign a function to them like this:
$(".parent_div INPUT[type='checkbox']").
change(
function(){
var child = $ ( this ).
parent().
next( ".child_div" ); $ ( child ).
children ().
change (
function (){
alert (
"changed"
); }); });

It will work, the function get"s assigned to each checkbox in the div. Why my boxes are not getting checked? On a side note I found this curious, if I try to access the checkboxes by specifying a selector type in the children method like this :
$( child ).
children ( "INPUT[type='checkbox']" )
or
$( child ).
children ( "input" )
It doesn't select the boxes. In case anyone mentions it I know that the child divs are not actually children of the parent divs, all these values are coming from a database and the names were chosen based on the database relationships.