I think markers would want that you adress the issues or themes which are present in your prescribed text in your related text as well. But, if you really cannot find any other themes, maybe try integrating some of the information into the 2nd related text, or simply compare how the themes may differ, how it offers provocative insight and is thought provoking, how it differs from your first two texts of belonging or not belonging. If you can integrate, or rather compare your texts, providing an insightful, though provoking theme which simulates the marker, then it is fine. Otherwise, you will benefit more from adhering to the universal themes/issues.
Hope that helps!
Am currently in year 11, but have already started learning belonging