Some time ago, I merged two story lines. In doing so, I created a problem with two characters having the same name. This later became a problem with another of my story lines. I recall mentioning this in the past, but decided to address the subject again.
My solution was to create a list of first and last character names.
When I create a file of story data for a new story I add my list of character names to the story data, and then select a new character's name from the list and delete the first and last names from my story data file.
In creating the list, I searched the Internet for lists of first and last names and added them to a spreadsheet using two columns for first and last names. I then sorted each column of names and deleted duplicates of the same name. I then randomized the list of names, so I wouldn't be picking the in alphabetic order. I now have a master list of first and last names that I use to select character names for my stories. The only problem I now have is with the older stories. my list of names occasionally contains the first or last name of an existing character.
Do you have this problem with your character names?