I have some Kentucky Cain relations. Patrick Cain from Ireland settled in Nelson Co & later Grayson Co. Have been able to establish a connection with other Kentucky Cains (and disprove connections with some) by comparing Y-DNA through the Cain DNA Project at www.familytreedna.com/public/Cain-Caine
Y-DNA also proved Irish origins. Indeed, Y-DNA narrowed Patrick's probable place of origin down to a small cluster of parishes in Co Galway. Some other Kentucky Cains have proven via Y-DNA to have Ulster origins. They are the biggest group in the Cain DNA project.