Looking at your Browns in the 1850 and 1860 censuses, it's clear from their children's birth locations that they had their first two children in Ohio, then two in Kentucky, then one in Ohio, then one in Indiana, then back to Kentucky, then back to Ohio by 1860. Allen was born in Kentucky and Cynthia in Ohio. They are probably not connected to the Brown family in Highland Co. since the group described in the Ayres book sounds like it was there for a while. I'm guessing Kentucky would be the place to look for them.