In your FFXIV folder (C:\Users\"you"\Documents\My Games\FINAL FANTASY XIV - A Realm Reborn) you should have a folder for each character that looks like FFXIV_CHR with abunch of numbers and letters after it. Log into one of the characters and then log out, and see with folder's files contain the most recent Date Modified so you know which folder is for which character. Then copy all of those DAT files of the character you wish to copy to the new character.