Let's say you have a friend, who has a former friend turned bitter enemy.
Then perhaps you meet someone who seems to have a lot in common with you and there is an interest in perusing a friendship, so you exchange names and numbers. While speaking with this new potential friend she mentions a friend of hers who has a story very similar to a friend of yours, who has an enemy with the same first name of the person you are now speaking to.
Dun dun duhhhhhh.
Do you find out for sure the last name of the enemy? To you go on speculation?
If it's the same person, do you avoid the new friendship out of respect for you more established friendship?
Do you continue with the new friendship, careful to never mention knowing the other?
Is there a graceful way to be friends with both?