My ancestor Adam BLACK / (SCHWARZ) had a daughter Mary BLACK/SCHWARZ, born say 1766 who married a Mr. SIGHTS, and was called Mary SIGHTS in his will written in 1789 in Rowan County. Her husband may have been Jacob SIGHTS, who was a witness to a deed in 1796 in Stokes County from Adam's widow Sarah to their son Frederick BLACK.
SEITZ/SIGHTS researchers generally list the wife of Jacob SEITZ/SIGHTS as Mary Elizabeth PRESTON. This site:http://freepages.genealogy.rootsweb.com/~harrisonrep/Johnson...
states that a KY history lists his wife as Mary PRESTON, and an Illinois history lists it as Mary BLACK. This Jacob went to KY and then to Illinois. I wonder if perhaps Jacob had two marriages, one to Mary BLACK, and another to a PRESTON.
You can see information on my SCHWARZ/BLACK family at:http://home.netcom.com/~fzsaund/black.html