We've extracted all the BARTLETTs in the KY census up through 1880.Based on this, your Reuben BARTLETT b 1770-80 was in Bracken Co, KY census 1820 and 1830 before the Clermont Co, OH 1840 census (I can 't find him in 1850 census). Based on census records, he had 8 children and your Solomon b c1825 and John M b 1821 fit right in.
There is an Isaac BARTLETT in the Bracken Co, KY 1800 Tax List, but I haven't extracted any other Bracken Co, KY tax lists to see if there might have been a connection.
Based on a recent World Connect post, Reuben BARTLETT was born c1784 in MA, but I haven't been able to trace any of his children to the 1880 census to confirm that.
Do you have any male BARTLETTs from this line who would DNA test?This test would probably indicate which line is yours - we already have DNA on file for several different BARTLETT lines from MA - a match would confirm it and give you a solid place in MA to look for your link.If you have time, you may also want to trace the Bracken Co, KY tax lists 1800-1820 - using the Morman's microfilms through any Family History Center.