Impossible at the momentPreviously this was impossible, as one of the merged questions (the source) iswas literally destroyed -- it doesn't exist any more.
A merge record is recorded in the history of the target question, but it's not in any kind of reasonably queryable format.
It sounds to me like you're arguing for keeping the duplicates, closing as duplicate, and just shuffling the answers around, which is a different request.
Merge is for PERFECT duplicates.
edit: weWe now handle question merging in a much more sane way -- both questions are retained, one is a stub, and all answers are migrated into the merged question. If the stub is deleted, we 301 redirect to the merge target.
https://blog.stackoverflow.com/2010/06/improved-question-merging/
(nothing Nothing can be done about old merges, sadly, due to our poor choice to destroy the other question in the merge)