Daughter Peggy seems to be the oldest and assuming Scarborough at least 18 when Peggy born, then his birth year would be no later than 1755.  Although Scarborough could have been much older than Rachel, it is likely he was just a few years older than her and so was his earliest birth year was probably not much before 1740.  It is possible that Scarborough Jr. is the oldest but I have not given that as much thought yet. Scarborough's will was apparently written on March 25, 1795 and he is mentioned as deceased by June 22, 1795 (Order Book #16 - 1792-1795, pp. 438&439).  It is therefore likely his death was in June of 1795.

Assuming Rachel at least 12 when Peggy born and no more than 40 in 1786 (assuming William was last child), then Rachel's probable birth 1745-1761.  Her death must have been before son Charles was stated to be an orphan on April 25, 1796.

Peggy:
Dec. 28, 1785 married James Saunders in Brunswick Co. (at least 12?)
Had son Scarborough Saunders old enough in 1795 to be given slave (10-12?).
Probable birth 1765-1773.

John C.
2 Apr 1793 married Milly Fleming in Halifax Co. VA.
Probable birth 1765-1775

Freeman Dorsey
12 Jan 1797 married Jenny Fleming in Charlotte Co. VA
Probable birth 1769-1779

Francis
Married Catherine before Nancy was born on January 07, 1793.
Died February 09, 1797
Old enough to have estate in 1797-at least 21?
Probable birth 1763-1773

Delphey
18 Sep 1798 married James Hill in Brunswick Co. VA.
Not of age in 1795 according to Scarborough's will.
Chose guardian June 26, 1797-at least 12?
Probable birth 1783-1785

Thomas
25 Oct 1798 married Mary Fulkerson in Halifax Co. VA.
Not of age in 1795 according to Scarborough's will.
Did not have guardian March 27, 1798-over 21?
Probable birth 1774-1777

Scarborough
He may have married Polly Pamplin on Jan. 7, 1800 in Charlotte Co. VA which might indicate a probable birth of 1772-1782.  Or he may been the Scarborough who married Phoebo Lockett in 1790 which might indicate a probable birth of 1762-1772.

William
He may have married Dorothy Coleman Oct. 15, 1810 in Brunswick Co. VA
Had special guardian March 27, 1798-under 21?
Probable birth 1778-1786?

Charles
Orphan April 25, 1796
"Bound out" April 25. 1796-at least 14?
Chose guardian June 24, 1797-at least 14?
Had special guardian March 27, 1798-under 21?
Probable birth 1783