I am descended from Isaac Revelle. From what I can tell, Nancy had two younger brothers, William A. Martindale b 0ct 1868, and Adam Newton martindale, b Apr 1878. So she was at least 12 when orphaned. She was listed in 1880 as an orphan in the household of Isaac Calvin Revelle Sr. It is unclear the exact relationship between Isaac Revelle b 1823 and Nancy's grandfather Joel revelle, b 1824. You can bet they went to school together and such, but were not brothers or even first cousins.
1880 Census Information for Isaac Revelle: E.D. 59, St. Michael Township, Madison County, Missouri, House number 9/9, Page number1
Names Rel. Color Sex Age M. S. Place of birthFather's b-place Mother's b-place
Revelle, Isaac Head W M 56 M MissouriNorth Carolina North Carolina
Revelle, M. C. Wife W F 24 M MissouriMissouri Tennessee
Revelle, E. A. Dau W F 20 S MissouriNorth Carolina Virginia
Revelle, Franklin Son W M 18 S MissouriNorth Carolina Virginia
Revelle, H. D. Son W M 4 S MissouriNorth Carolina Tennessee
Revelle, Corah E. Dau W F 4/12 S MissouriMissouri Tennessee
Martindale, Nancy Orph W F 13 S MissouriMissouri Missouri
Are you related to the Pastured beef folks? I came across a pretty cool website about grass fed beef when I was researching this line a few years ago...