In the cast editing window find the actor you're looking for. In your case Tom Dugan. Highlight that actor and click in the Edit Cast Member option and in the Birth Year section enter the Birth Year.

Now to separate him from the other you need to add Tom Dugan again and either leave the Birth Year blank or add his Birth Year as above. Or if not known a fake one.

Of course you then need to edit any profiles with them to properly link the correct actor to their correct films/profiles.

If contributing any new Birth Year you need to document why and where the year came from, usually with website links.

Quoting CubbyUps:

Quote:
Or if not known a fake one.

What I do when I can't find a birthdate as I don't want fake data in my database is to place the complete name in the first field.

So I have two, by exemple, Tom Dugan.

1. Tom Dugan
2. Tom Dugan ---- -----

So no false information, just a different format and each name form come when I do a names search

edit : Too bad it's impossible to do the same with the two other fields as it would be possible to have four actors with the same name with no fake data when no birthdates are available...

1. Tom Dugan
2. Tom Dugan ---- ----
3. ---- Tom Dugan ----
4. ---- ----- Tom Dugan

Quoting Lewis_Prothero:

Quote:
Starting with (e.g.) 3000 will give you the opportunity to add 7000 duplicates of the same name.

Actually the BY-field can take values up to 65536, so even starting with 10000 you'll get more than 55000 possible duplicates...

Quoting Lewis_Prothero:

Quote:
Why so complicated?

Because I like complicated
Even a random number can't please me as it's a wrong information. Of course if the field was named something else than birthdate I would be happy to just wrote 1,2,3,etc., but as it is its name for me this sound wrong.