This is a strange family - I can't find Nathaniel in the 1870 or 1880 census. Have you found him in the census? I found him in 1900 census saying his father was b MS; mother b AL
There are very few Nathaniel BARTLETTs in VA.
Could his middle name have been BARTLEY?There is a Nathan Timberlake BARTLEY b 1842 VA was in 1850 Orange Co, VA census.
Neither can I find James or Franklin SISSON b 1852 (some report him as father of Nathaniel) in any census 1900 or before.
Mary JOYCE, Nathaniel's wife, is in 1880 White Co, AR - there are no SISSONs of any spelling that I can think of his White Co, AR in 1880. Neither is there any likely Nathaniel in White Co, AR in 1880...