William, (I'm assuming it's William and not illiam!) I looked through all my books but didn't find anything. Sorry. I tried to find then on the census but only got back as far as 1870. Coulnd't seem to locate them for sure beyond that. I am assuming that they were in Indiana by 1855 at least. I did find a few marriages on Ancestry that might be the sons of Benjamin. Richard L. Lewis to Lucinda Tatum, 2/1/1864 Bartholomew Co., IN, bk C-7, p. 169 John Lewis to Susan Weaver, 8/13/1857, Clark, bk. G, p. 253 William Lewis to Lucy Hooper, 9/27/1857, bk. G, p. 264
One suggestion might be to get a copy of a death cert. for one of Benj. & Mary's children and see if it lists where in KY they were born. Do you know when any of them died? How did you get Mary Ashby's last name?
I think your assumption is correct that the marriage of Benj. and Mary took place in KY--but where. I wish I could locate them on the census in 1850. They don't seem to be in Indiana, as far as I can tell.