This is not my Erwin line, but I wanted to see if I could be of help.
Findagrave.com shows the burial information for Landon H. Erwin to be in Martha Cemetery, Jackson Co. OK.The information shows:
Landon H. Erwin, b. 10 Aug 1902, d. 7 April 1912.The information identifies him as son of William A. and Nancy A. Erwin.
I live in Oklahoma and I became interested in why this 10 year old boy, who was in Alabama in 1910, was buried here, so I looked for possible Erwin family in the area.Harmon Co. OK borders Jackson Co., and in 1910, I found Dock Mack Erwin, b. TN, living in the area of Gould, Harmon Co.Gould is only about 4.7 miles from the town of Martha.
Further research shows this man was from McMinn Co. TN.His given name was unusual, Doctor McWhirter Erwin.He probably went by Mack.He was a son of Joseph Darius Erwin, of McMinn Co. TN.Joseph D. had a brother, Louis Erwin of McMinn Co.This Louis Erwin had a son, William, born 1859, TN, in all probability in McMinn Co.William A. Erwin named his first son William Louis Erwin.I know this is not the same as birth certificate or death certificate information, but it is strong circumstantial evidence, and I believe Louis and his wife, Sarah, were the parents of your William A. Erwin.William A. and Dock Mack Erwin would have been first cousins.So it would appear, for some reason, Landon was sent to live with his father’s cousin.
D. Mack Erwin homesteaded 160 acres in Harmon Co. OK in 1906.His name on the land record is Doctor M. Erwin.Burial information for him and family members can be found at findagrave, although his name is misspelled Dock Mock Erwin.