Hello. Has anyone written a dual biography of Charles Dickens and Guiseppe Verdi? Both were born at roughly the same time, both wrote with a profound understanding of human nature, and both had the same restless nature.
If I were to write something, how would I get started and what to do about accuracy? Could I take a little liberty and imagine a conversation between the two?
I don't know if this has been done, but the short answer is that you can do virtually anything in fiction with historical figures.
Assuming you want to portray these men as accurately as possible, you will obviously need to do your research. That's probably your starting point.
Did these men have a relationship in real life? Even if they only corresponded, you could use their letters as the basis of a fictional conversation. If not, you could use your artistic license to envision a fictional conversation between them.
It strikes me that this might make for an interesting play -- provided you can construct a solid dramatic arc based on a problem they are trying to solve or an issue they need to address. There's no plot without such a challenge, and no story either.
So that will be your second challenge -- finding what the story will be about. Two men meeting = dull. Two men coping with a challenge = a story (even if that challenge is purely internal or philosophical).
Best of luck.