I've been working a little on this same problem. Mildred Alba Mosby is the daughter of Poindexter W. Mosby and Nancy Sledd. I think that Poindexter W. Mosby must be the son of Poindexter Mosby married to Mary Woodson but haven't been able to prove this yet. This is what I do have.
Poindexter W. Mosby married Nancy Sledd (daughter of John) Dec 25, 1815 in Bedford Co. Virginia.
Poindexter W. Mosby died about Dec 1845 in Bedford Co. Virginia.
Nancy Sledd was born 20 Oct 1798 and died 21 Aug 1859. She is buried in the Mt. Ayre cemetery in Pike county Missouri.
Children that I know of are:
1. Mildred Alba Mosby b. 1817 married to John W. Turpin Dec 12, 1837 in Bedford co. Virginia. died 5 Jan 1861
2. Catherine E. Mosby married to Walker R. Ogden on 29 Dec 1841 in Bedford co. Virginia
3. Elizabeth Jane Mosby married to Henry Salling on 19 May 1845 in Bedford co. Virginia
4. Littleberry Walker Mosby b. 28 Jan 1830 in Bedford Co. VA and d. 7 Dec 1861 and is buried with his mother in the Mt. Ayre cemetery in Pike co. Missouri.
5. Zebulon W. Mosby b. 1832 d.1902 married to Catherine Turpin sister of John Willis Turpin
6. Sarah Virginia Mosby b. 1838 married to John A. Edwards in 1859
After Poindexter W. Mosby died in Bedford co. VA his family moved to Missouri along with some of the Turpin family in 1847.
I believe that he also had a brother named Powhatan Mosby.
If anyone can prove or disprove that Poindexter W. Mosby's parents were Poindexter Mosby married to Mary Woodson it would be greatly appreciated.
I hope this helps. I am descended from Mildred Alba Mosby =>Woodson Morris Turpin=>Homer Reid Turpin=>Helen Ruth Turpin