There is a birth record for Mary Eastman in Corinth, Vermont, daughter of Josiah and Rachel Eastman, born on December 5 1804.  There is also a record for a Nancy Eastman born in the same place on March 21 1807, also a daughter of Josiah Eastman.  In the book "150 years in the Dales and Hills" by Milton Ferguson, Nancy Eastman is described as being the daughter of Josiah Eastman and Rachel Holden.

     Thomas Munsell (Junior) married Mary Eastman on September 7th 1823, in Licking County, Ohio.  In 1820, Josiah Eastman is living only six houses away from Thomas Munsell (Senior).  Josiah has two daughters aged 10-16, the right age for both Mary and Nancy.

    Thomas Munsell (Sr.) and Josiah Eastman were some of the first settlers in Licking County, Ohio.  They both came there in 1815 with their families.  In Corinth, Vermont, Josiah's wife's name was Rachel.  In Licking, Ohio, there are death records that show that the name of Josiah Eastman's first wife was Rachel:

ixc. Eastman, Josiah, died Apr. 28, 1868, aged 90y 2m
ixd. Eastman, Rachel, wife of J. Eastman, died Dec. 25, 1823, aged 44y
ixe. Eastman, Abigal, wife of J. Eastman, died Apr. 24, 1877, aged 94y

     This shows that Josiah and Rachel Eastman of Licking County, Ohio are the same as the Josiah and Rachel Eastman of Corinth, Vermont.  This also means that Josiah and Rachel Eastman did in fact have a daughter Mary who came with them from Vermont to Ohio, and who would have been in the right age range of the Mary Eastman that married Thomas Munsell (Jr.) in Licking, Ohio.  Considering that Eastman is a unique name, and that they were living only a few houses away from each other, makes this almost certain.

     Mary would have had two sisters, among possibly others;  Rosina, who married Elisha Belknap, and Nancy, who married into the Alward family.  Josiah is living with his daughter Rosina's family in both the 1850 and 1860 U.S. censuses.  Both Belknap and Alward families are living near Thomas Munsell Jr. and Mary Eastman in the 1830 census.

     In the History and Genealogy of the Eastman Family in America (1901), it is mentioned that Josiah, the son of Edmund and Mary (Davis) Eastman, went to Ohio from Corinth, Vermont.  Josiah's death record in Ohio puts his birth date roughly two months before April 28 1778.  There is a birth record for a Josiah Eastman in Corinth, Vermont on March 1 1779, with his parents Edmund and Mary.  Although there is a year's discrepancy between these two dates, these are very likely Josiah's parents.  Dates were often recorded as, for example, 1778/1779, so the actual year my have been 1778.