JQuery :: Form Submission To Two Actions

I've got a form that I need to go to two different places. First, I need it to submit a portion (but not all) of inputed data to one url (url.php). If that is successful, I need it to submit another portion of the inputed data to another url (url2.php). The trick is, I need the information from some fields to go to both places, but with different names.

Here's what I'm doing:
$(function() {
$('form').submit(function() {
return false;
$.ajax({
type: "POST",
url: 'url.php',
data: $('.string').serialize(),
success: function(){
$.ajax({
type: "POST",
url: 'url2.php',
data: 'firstname='+$('#Contact0FirstName').val()+'&'+'lastname='+$('#Contact0LastName').val()
});
}});
});
});

I have the information I need to go to url.php serialized by class (.string). Then, I try to make a string out of the data for url2.php. What seems to be happening the form is submitting ALL fields to url.php, ignoring the serialized string I told it to use, and then submitting ALL fields to url2.php, again ignoring the string I told it to use.