You may already have this information.
The answer to the request about the two Thomas Olivers was not found.
My suggestion is to send requests for the death certificates. My
favorite aids are the census and land records this might identify
children when a parent dies.
The Bureau of land management site is so helful. Their address is:
http://www.glorecords.blm.gov/
The Oliver families applied for their land in 1837 and 1839,
lived in Johnson Twp., LaGrange County and are buried at Woodruff
Cemetery. (LaGrange Co. cemetery book)
James Oliver born in 1823-found his passport to go to Roxburyshire,
Scotland in 1885. It gave his age and physical features. James and
his wife Susan moved to Mishawaka and later South Bend, IN. James
started Oliver Chilled Plow works. see adddress to verify.
http://www.centerforhistory.org/ocpw.html
Oliver Lake was named after James Oliver. Found info on the Oliver
Lake history.
1860 Census-Entry # 356, Thomas age 49, wife Emily age 50
Children: Lewis age 22, Thomas age 16, Melinda age 11, Volaau ?, age 7
Entry # 357, Thomas Oliver, senior, age. age 89, born in North
Carolina. Mary age 90, born in VA. Another census had him born in
Scotland.
Hopefully something in this message will be helpful.