Shannon, My latest theory is that Lewis A. Blake, along with Jonathan and Amanda, were the illigitimate children of Jane Blake, who was a daughter of William Blake Jr. who married Mary Ochiltree.
My source for this is Greenbrier WV Heritage 1997, by S. Grose. On page 32,under the entry for William Blake Sr. (m. Hannah) it says "Their known children were William Blake, Jr. m. Mary Ocheltree in 1792. Their children were: . . .Jane b. ca. 1796, never married (had children)." You can find the book through Google books.
Jane was mentioned in the will of William Jr. written September 1831, where she is referred to as "Jane Blake."
When Amanda dies in 1871, her parents are listed as "Lewis and Jane Blake" and the informant at Lewis Blake, father. I am suspicious of this entry because of the ages of the other men named Lewis Blake in the 1870 Greenbrier census; the oldest is about ten years younger than Jane and likely couldn't have fathered Lewis A.
So, as far as fathers for Lewis A, Jonathan and Amanda go, that leaves 3 possibilities:
a) an older, out-of-town Lewis Blake was the father and maybe informant; b) a VERY young Lewis Blake had a relationship with Jane; c) the clerk made a mistake and the informant was Lewis, her brother, not her father.