I have found some more info that may help some of us figure out our Cains in Cumberland CO KY.
William Cain md Hannah Stanfield in 1790's in Surry NC, in 1800 census he had 1 male 0-10 2 males 26-45 , 1 female 0-10 and 1 female 26-45, this in Surry. In 1810 Cumberland Census he had 1 male 0-10, 2 males 16-26 and he was over 45, he had 1 female 0-10 and 1 26-45. So at this point he had 3 males in house and 1 daughter, in 1815 Lucinda Cain md Joel Claywell, in 1823 Thomas Cain md Margaret Claywell(siblings). THese 2 families left Cumberland after 1830 and went to Scott Co Illinois. Thomas died there 1833, leaving Margaret a widow. Lucinda lived a long time. So Thomas is still there in 1830 census also younger William Cain and a Rhoda Cain. Also in Surry in 1800 was a Russell Cain and a Tice(Mathias) Cain. In CC Ky 1810 is also a Ben(Benjamin) Cain, he md Rebekah Stanfield, Hanna Stanfiled sister. They are only in CC Ky in 1810, they had 2 males 0-10, 1 male 10-16, 1 male 16-26 and one 45+, s females 0-10 and 2 10-16 and 1 45+. A benjamin Cain can be found in Warren Co Tn in 1820, he has 2 males 0-10, 1 16-18 and 1 45+, females 1 10-16, 1 16-26, 1 26-45 and 1 45+. Also there is a John Cain who has 1 male 0-10, 1 18-26 and 1 26-45 and 1 female 10-16. I have found where he came there aboput 1815 and was in Tombstone and Bible records as being the son of William and Hannah Cain, he md Beersheba Porter Sullivan, John died in 1830's. Robert B Cain is there 1850 census, he is reported to be son of William and Hannah Cain b 1808 Ky. He md first Mary Lawrence 1831 in Davidson Tn, she the dau of William Pitt Lawrence and Nancy Pomeroy. She died by 1836 and he md Tebitha C unknown. Robert died in McMinnville Tn 1889. Roberts dau Mary md James Camp, she was his second wife as had md Laura A Cain first she died and he md Mary. Laura was the dau of John and Beersheeba Cain.
So it looks as if Benjamin left CC Ky after 1810 and went to Warren Co Tn and Williams' possiblle sons Robert B and John went too. Since Williams remaining children went to Scott Illinois after 1830, this appears to take this entire migration of Cains out of CC KY before 1840. he only questions remaining then are who is thew Rhoda Cain in
1820 CC Ky, she has 3 males 0-10, 1 10-16 and 2 females 0-10,1 16-26 and 1 26-45. She is not there in 1830. I found this Mathias Cain md Rhoda Goodman( daughter of Batlett Goodman) 1794 in Bedford Virginia, I do not know if this is the same Mathias in 1800 surry NC or the same Rhoda in 1820 CC Ky, but is worth looking into. In additionin 1840 Scott Illinois is a Bartlett Cain who came there from McMinnville Tn about 1833, he had sons William Bartlett and Benjamin C Cain. He went on to Wisconsin after 1850.
I will continue this message on another message as I seem to be trying to get kicked off.