Martha is listed by George D. Blakey as daughter of Richard Duncan - I'm assuming these are her parents. She was probably a few years older than indicated by her birth - I doubt that she married at age twelve.
Martha Penelope DUNCAN and Dr. Thomas H. GRUBBS were married on 12 February 1850.859 Dr. Thomas H. GRUBBS817, son of Thomas GRUBBS and Sarah C. BAGBY, was born on 1 July 1820.112 He died on 23 June 1877 at the age of 56.112
1860 Census. Logan Co KY, Dist 1, Hh 1109
1870 Census. Russellville, Logan Co KY, Dist 107, Hh 91
Martha Penelope DUNCAN and Dr. Thomas H. GRUBBS had the following children: