I found records of a Nathaniel BLACKSTONE (born 1771 in Maine, died 13 September 1856 in Maine), son of Benjamin BLACKSTONE (1725-1799) and Eleanor PHIPPS (1729-1816). This Nathaniel is listed as the brother of Captain William Henry BLACKSTONE (1766-1850) [married to Barbara FARR], Samuel BLACKSTONE (1766-1846) [married to Hannah PETTINGILL], Soloman BLACKSTONE (1772-????) [married to Nancy UNDERWOOD], and Sarah BLACKSTONE (1778-1851) [married to William BUCKNAM].
Nathaniel's father's parents are listed as Benjamin BLACKSTONE (1699-1763) and Mehetable HUNT (1705-1763), and Nathaniel's mother's parents as Danforth PHIPPS (1709-????) and Elizabeth SKILLINGS (1713-1786). A quick glance at the tree shows that the Blackstone family line recorded with sources can be traced back as far as 1543, though I'm not sure how accurate these records are. From what I can see, however, all of Nathaniel's ancestors have been connected on this tree for quite some ways—clearly, your family is well sourced!
Nathaniel BLACKSTONE is listed as married to Apphia MERRILL (1772-1849). Their children listed include Sarah BLACKSTONE (1795-1867) [married to Edward Wilson MERRILL], Nathaniel BLACKSTONE (1797-1852) [married to Mary SAWYER], Ann BLACKSTONE (1800-1847) [married to William DECKER], Stephen M. BLACKSTONE (1803-????) [married to Susan WARNER], Joseph BLACKSTONE (1805-1883) [married to Sarah Jane STURTEVANT], Benjamin BLACKSTONE (1805-1894) [married to Mary Ann GOODELL], Elizabeth BLACKSTONE (1810-1818), and Francis BLACKSTONE (1812-1872) [married to Hannah STURTEVANT].
Here is the link to the FamilySearch profile: https://www.familysearch.org/tree/person/details/LH1K-GQC
I'm unsure how much of the information is correct and sourced, but hopefully if this is the correct Nathaniel it gives you a good jumping point!