Thank you for helping out. My great great great grandfather, Cary Duncan, did have a son by the name of Robert Duncan born about the same time as your Robert Duncan but it looks as though they are not the same.
Cary Duncan and wife Lucy had 9 children. Daughter Lydia Duncan married George W. Newton. Their daughter Eliza J. Newton married your George W. Duncan. I am unable to locate anything on George past the 1920 census. I did try searching what cemetery records are available online for George or Eliza but have come up blank.
Of George and Eliza's children, I am unable to find several of them past the 1920 census.
1st child was Robert Duncan. He is in 1880 census in Lewis County, VA but after that nothing.
2nd child was Willie Duncan. She married John L. Wright in 1893 Henry County, IN. They had one daughter Hazel Wright. Hazel married Harry Cebert Walter and they had the following children: Cebert G. Walter 1917, Gale Walter 1919-1979, Rose Mary Walter 1921, Virginia 1927 and Leland 1928. I am able to find Willie all the way up to 1930 census.
3rd child was Thomas Duncan born 1874. I can find him in 1880, 1900, 1910 and 1920 census but not 1930. He married Myrtle Byrum(?) in 1900. The had the following children: Goldie May born 1905, Jessie James 1907-1974 and Pauline born 1915.
4th child was Dallas Duncan born 1877. He died 6 Feb 1892 in Mooreland, Henry County, IN.
5th child was Emmaline Duncan born 1879. I have not found any record indicating she ever married. In 1920 she is living with her brother Claude. In 1930 I found what might be her living in Wayne County, IN as an inmate in Wayne Co. Infirmary. Her name is listed as Emma Duncan born in Indiana but parents born in Virginia.
6th child was Claude Duncan born 25 Aug 1882 in Lewis Co., WV. He married Christina Perkins. They had 3 children, Erma born 1909, Mabel born 1915 and William born 1918. Claude and Christina are in Wayne Co., IN up to 1920 census. I can not locate Christina or children in 1930 census. I have a possibility of Claude in 1930 census. There is a Claude Duncan living in Fayette County, IN. His age is listed as 48, married and born in West Virginia. He is listed as a roomer with another family.
7th child was Hugh Cleveland Duncan born 1884. I have found no record of a marriage. He is in 1900 and 1910 census in Wayne County, IN but no record of him after that.
8th child was Ralph Duncan born 1885. Able to find Ralph in 1900 and 1910 census but not 1920 or 1930. In the Indiana Marriage Records it shows he married Bessie P. Rickner in 1916 but that is all I can find.
I do not know of any direct descendents of George and Eliza that are still living. Sorry. If you can add anything to this please let me know.