This would take a bit of work... but you could:
1) Add another (birth, whatever) fact
2) Copy the "best" citation you want to have in a report and paste it to this new, fact.
3) Right click the new (birth) fact and select to make this one the preferred one
4) Mark the "old" fact as private - right-click > private
5) choose to not include private facts.
You can make different facts private or public, but not different sources.