I see he was discharged from Co D, 48 OVVI during the Civil War for disability. He is listed as wounded at the battle of Ft. Blakely, Alabama, April 9, 1865 - which is a year after he was discharged. That's rather odd. (You can check this at my web site:
www.48ovvi.org see the rosters and appendix to the regimental history) If you find out why he reappeared after being discharged please let me know so that I can make a note of it on the web site. Also, if you'd like to write a bio for him I would be pleased to add him to the Veterans section of the web site.
You might try getting his invalid pension file from NARA. His widow may have applied for a pension as well. Usually there is some form of proof of birth in these files that may include parents' names. They are almost always worth the investment.