It's possible with the linked questions API call, but you'll need to do some work to filter out the real duplicates (as opposed to question which are merely linked by mentioning the original question in posts or comments).
The default filter includes a
closed_reason which will have the value
duplicate, but it could be that it's closed as duplicate of another question. Therefore, you need to add the
closed_details to the filter:
and check the
original_questions element. For example, to find the many duplicates of Editing a post during review doesn't show an "edit not possible" message you can call the following URL: https://api.stackexchange.com/2.2/questions/298797/linked?order=desc&sort=activity&site=meta&filter=!9Z(-wvHE( and look for its