1870 Census District 7, White County, TN shows he is living with his mother and James ... they are living in her parents' household, along with her brother and niece.
1880 Census District 7, White County, TN shows Samantha re-married to James Kelly, with the 2 Crowder boys (listed as Kelly), son Samuel Kelly, her mother, brother and niece.
Possible 1900 Census District 14, DeKalkb TN shows Thomas, bn Jan 1868, single, with 2 boarders, one is Fred M Kelly? possible half brother?
Possible 1900 Census District 7, White County, TN shows Thomas Kely, bn Jan 1867, widowed, living with parents James and Samantha, brother Frederic and a niece.
I think he was enumerated twice in 1900. The counties are neighboring in Tennessee. White County lists his occupation as Fireman at the sawmill, while the one in DeKalb county lists him as an engineer. Both Censuses seem to show his half-brother Frederic.
Marriage record: Fannie Saylors 23 Aug 1889, White County, TN
Suggest further investigation in White County, TN.