Group Similar nodes in XML using XSLT

Question

I have the following XML structure

<?xml version="1.0" encoding="UTF-8"?>
<Root>
    <BookingGroup>
     <PostCodes>
      <PostCode >AB</PostCode>
      <PostCode >AL</PostCode>
     </PostCodes>
    </BookingGroup>
    <BookingGroup>
     <PostCodes>
      <PostCode >AB</PostCode>
      <PostCode >D</PostCode>
     </PostCodes>
    </BookingGroup>
</Root>

Now for every post code AB in the entire Xml I need the output as:

<Root>
    <Child>
        <Child1>
        </Child1>
        <Child1>
        </Child1>
</root>

because there are two AB postcode I need two child1 elements.