Hereís the information you requested:
Cemeteries of Brown County, Illinois
Mt Sterling Cemetery
Austin, son of O. P. and M. C. Gentry 27 Nov 1875, aged 1 yr
Oliver P. Gentry 20 Dec 1870 aged 55 yrs, 11 mos.
James M. Gentry [No Dates]
The family relationships section says Austin is the son of Oliver P. If this is really true then one of the dates has to be wrong. Austin was born almost four years after Oliver died. So I checked the 1870 Census.
1870 Census of Brown County, Illinois, Cooperstown Twp.
Oliver P. Gentry 55 m farmer Kentucky
Martha A. Gentry 53 f Kentucky
James A. Gentry 14 m laborer Kansas
Oliver P. Gentry Jr. 30 m farmer Illinois
Margaret Gentry 26 f Ohio
William Gentry 9 m Illinois
John ?. Gentry 3/12 m Illinois (b. Feb)
Johnís middle initial was not readily readable. It could have been an O or P or even Jr.
This also fixes the date problem and you can also see Austinís motherís name.
Jamesís middle initial is a problem but Iím sure itís the same James as in the Cemeteries book.
The 1880 census does add much and some additional name confusion. It appears that both James and Martha (his mother) died before 1880. However, Martha could also have remarried and lived longer and been buried under her 2nd married name.
Hope this helps.
In your Permanent Residents index on page 216 your showing 5 names that I believe I'm related to. The surname is GENTRY. Thier first names and/or initials are: Austin, James M., M.C., O.P., and Oliver P. Any other information like dates or anything else would greatly be appreciated.