JQuery :: OnBlur Textbox - Closest Span Not Recognized

My HTML looks something like the following:
<label for="myTextBox">
Name:<span style="color:red;">*</span>
<input type="text" id="myTextBox"></input>
</label>

In my document ready I have a function which runs 'on blur' of the textbox and hides the span. The following code DOESN'T work to hide the span:
$('#myTextBox').closest('span').hide();

I'm currently using the code below which does work but was wondering why the above code doesn't....
$('#myTextBox').parent().children(':first').hide();