Parents:
Isham Jr. and Edith Edy (Lane) Blankenship

Isham and Edith removed to Blount County, Tennessee in 1799 after selling land in Franklin County, Virginia. Isham died before 5 Dec 1836 leaving heirs in Monroe County where his children are named in a court order. Isham's 1836 Will, Vermillion, Illinois Wills and Probate, names:
first wife unnamed;
son William Blankenship;
son in law, Samuel Purcell;
Calvin Stearns. (Alameda Stearns, daughter-in-law to William).

Marriage
1) Polly Whitsett
2) Elizabeth 'Betsy" Chambers, 24 Jan 1811 in Jefferson County, Indiana.

Children by Elizabeth Chambers:
Sally Blankenship 1811– m. Samuel Purcell, Vermillion, Indiana
Aley Alice Blankenship 1813–1883, #184399732, m. Dennis Murphy, Vermillion, Indiana
Avery Blankenship 1815–1875 m. Priscilla Stutler in Vermillion, Indiana
William Chambers Blankenship 1818–1887 m. Almeda Stearns, Vermillion, Illinois
Alexander Chambers 'AC' Blankenship 1822–1897 m. 1) Sarah Reese, 2) Elizabeth Murphy, 3) Margaret Blackford
Rev. Martin Blankenship 1824–1857, #67470567 m. Jeraldine Scott in Vermillion, Illinois
Anna Blankenship Lane 1825–1903, #5544773 m. Orlando Lane in Vermillion, Illinois
Elizabeth Blankenship Bennett 1827–1865 m. Caleb Bennett in Vermillion, Illinois

Sources:
"Blankenship Ancestors" by Gayle King Blankenship (1995)

Comments by Contributor Thomas #46876300:
As stated in the will of William Blankenship d. 7 Dec 1836 his second wife was named Polly (Mary) who according to my records survived his death another 32 years. His first wife was Elizabeth Chambers. She and William were married 24 Jan 1811 in Jefferson County Indiana, ref. Ancestry.com source Indiana Marriage Collection, 1800-1941. Last child born to that union was William Chambers Blankenship, b. 1818, (memorial 26111035). William (memorial 181091236) was enumerated in Militia Township, Jefferson County Indiana in 1812 placing him in Jefferson County not too long after his first marriage. After the death of Elizabeth he married Mary Whitsett, who he referred to as Polly in his will. Their marriage was on 18 Oct 1820, in Jefferson County Indiana, ref Indiana Marriages 1802-1892 Ancestry. Com. Following the death of William Blankenship, Mary Whitsett Blankenship married Isaac Smith (memorial 128217500) on 2 Mar 1848 in Vermilion County Illinois, ref Illinois Statewide Marriage Index, 1763-1900, State of Illinois data base. Her name was recorded as Mary Blankenship. Isaac's first wife was Sarah Minerva Glaze, (memorial 82404183 ). She died 24 Oct 1845. This should prove the identity of Mary Whitsett Blankenship Smith.

Historical Notes on the Surname "BLENKIN"
"...in Normandy Before William The Conqueror went to England. Awarded a bounty of land along the Scottish border which he named "Blenkin's Hope" Lila C. Roche
An indication then that Blenkin was a trusted, reliable, and rather prominent soldier in William The Conquorer's [sic] forces, the Scottish border along the Roman Wall being a violently contentious piece of real estate and therefore deserving of bounty-ship to proven individuals. And the name evolved into Blenkinsop in England." [and into Blankenship in America].
Quoted from THE BLANKENSHIPS by Ernest J. Blankenship, Jr.