How to duplicate a page within a Structure?
There are two easy ways to avoid copying and pasting or having duplicate entries. 

First, you can use Globals to store the shared information.

Alternatively, your second entry/template can just ask for the data from the entry of the first entry.

{% set shared_information = craft.entries.slug('my-first-entry-slug').first() %}

&lt;p&gt;{{shared_information.customFieldWithSharedInformation}}&lt;/p&gt;