I don't know if it's of any help, but some people in my data base may be related. Per a Christian County KY Marriage Book, Nancy Black married Robert P. Alexander April 29, 1820, with Joseph Black's name also appearing (bride's father or brother?). Robert was about 21 or 22 at the time; so Nancy was probably of similar age.
I hope that our data connects. Post here or e-mail me.