I recently was contacted about James by a researcher doing the Wickwire family. James was the husband of Prudence Wickwire, daughter of Peter3 (Peter2 John1) Wickwire of New London, Conn. He wanted to know if I had additional information on his ancestry. We know a great deal about James for someone from 18th century northern Ireland. We have his exact date of birth from his family Bible record (July 18, 1759). We know his birth place from his tombstone ("a native of County Down"). And lastly we know he was a British soldier based on his pension records.
We can guess some more. There was a William Martin in the same regiment that may be his brother. We know his children's names and may hypothesize on possible parent names. However, the chance of finding the origins of James Martin is nothing short of what I would deem a genealogical miracle. Assuming he was Church of Ireland, since he married a protestant, are there church records still extant to prove a baptism with parents? Did someone transcribe his father's will prior to 1916? If not, that will no longer exists. So tying this man, with a fairly common name to his proper family in 18th century Ulster Ireland, is a bit of a stretch.
It is possible that he came from a middle class or even upper middle class background before joining the army. He was a surveyor, which is a profession. In any case, I've never explored secondary literature on the Martin family of Down, Ireland. You can get lucky sometimes. My Sinclair family from Antrim, married into the Lawrence Family which later produced a viceroy of India. Once that branch of the family was researched by Burke's, my branch just got lucky by being able to tag on back one or two common generations in the 18th century. Otherwise, I'm not how I would know anything before 1780 on this family.
I'm guessing the same might be true of the Martins, but I have yet to spend any research time for them. The first stop, should be the 1740 protestant householders' census, which would very likely have his father. That would also determine how many Martin families were in Down at the time.