Hi Kristin:
This is a hard question without seeing what you have. You have to have solid proof of your lineage from one generation to the next. Will's are a good source of proof. I have used tombstone pictures for the proof of death, you need to cite the exact location. Do you have proof linking the 3rd greatgrandfather to the 4thgreat? Is the 5th great the one you are trying to prove?
If you will provided a name for this ancestor, I can look in the Patriot Index to see if someone has already used his name for application.
This is a free lookup service privided by th DAR VIS Volunteers at this message board.
Regards
Laura