What is the proper salutation to use when sending a letter of condolence to two brothers; Dear Mr. Smith and Mr. Smith; or is it best to send 2 separate letters.
Personally, I would send two letters. However, if you want to send a joint letter, the plural of "Mr" is "Messrs" so it would be "Dear Messrs Smith". One question though - do you not know the brothers well? I'm assuming that if you're sending a letter of condolence, you are/were reasonably close to the deceased and his/her family. If so, then there is no reason why you shouldn't address the brothers by their first names.