Today I ordered Civil War and Revolutionary War documents for several ancestor's in my wife's family tree. If they come back, some might confirm the names of their parents, while others may reveal the names of their parents.
Sites
http://www.archives.gov/veterans/military-service-records/
http://www.archives.gov/veterans/military-service-records/pre-ww-1-records.html
Civil War
Henry Angle (1841-1926), parents unknown
Rufus Black (1836-1864), probably died in battle outside of New Orleans, parents probably Hiram and Polly but uncertain, also ordered pension file
Isaac Zeller (1839-1912), uncertain about his parents
Revolutionary War
Joseph Gallup (1725-1778), possible service in Revolutionary War, possibly died during battle