Still here and still searching for the connection. I have found John and Moses Tubb in Warren Co Tenn census. If I recall correctly, there was an age difference, but census would indicate they were brothers.
The earliest record I have is a marriage record of a Mary Tub to B. F. Boley in Missouri. The death certs of their four sons list her name as Mary Ross. I also have a marriage record of her daughter, Adaline Tubbs, to a Mr. Coat(e)s. Adaline's obit talks about her coming from Tenn to Missouri as a girl with her mother and two brothers (that would be James Monroe Tubbs and Issac Tubbs) which would likely indicate a move in 1860, which I expect is why I can't find them in the census records.
There is good reason to believe my Mary Tub(bs) is the Mary Ross in the home of Mastin (Martin/Marlin) Ross in Cannon, Co. Tenn in 1850. 1) She marries in Mo near a Charles Ross. 2) Charles Ross in Mo history book is son of Mastin and Nancy Ross of Tenn. 3) 1870 census has Nancy Ross living in Charles Ross home. 4) Adaline Tubbs (my Mary Tubbs' daughter) fits the same age as the Adaline Ross listed in Cannon Co. Tenn. She had a brother William at that time, who isn't mentioned past 1850 census. If Adaline traveled from Tenn to Mo with James and Issac, that would indicate William died in Tenn. Mary had 4 Boley sons (sidebar: George Boley is listed as a half brother in the home of James Monroe Tubbs in one census). That makes 7 for sure know children of Mary Tub/Boley. One of the census records lists her as the mother of 8 though. Again, perhaps an indication she is the same Mary Ross of Tenn making William the 8th child.
That is all speculation, or perhaps educated guess, but I have not found any real evidence to prove my Mary Tub/Boley of Mo is the same Mary Ross in Tenn. This is the hypothesis I am working. I have seen other researchers are working this as well.
Moses Tubb also has a will, and included in that is an amount of money to be given to an Adaline Ross and Monroe Ross ($200 each I think it was). There are census records that indcate James Monroe Tubbs went by Monroe, so perhaps there is a link. No relationship is giving in the will. A relationship to a nephew James Rains is listed as well as a sister Delphia Cummings. Given this will abstract, some have speculated that Moses was the father of Mary Ross' children, but perhaps not her husband. However, his will was executed in 1850 something, and Issac Tubbs wasn't born until 1860, so others have suggested it wasn't Moses but John Tubbs as the father of these children.
I am recalling this all from memory at the moment. If any of that is of interest I can point you to the documents. I would certainly be interested in any information you might have that would help hunt down the connection.