Hi Katherine -- Mary Jemison's family is as below (I don't have a source for it nor do I know how accurate it is.)
Mary Jemison, b. 1842-43, d. 1833. Mar. twice: Delaware Chief Sheninjee (Chenagee) and Seneca Chief Hiokatoo (Hokadowa).
By her Sheninjee the following children were born: a daughter, b. 1761, d. 2 days later; Thomas b 1762, killed by half brother 1811.
Thomas mar 4 times and had: By Squakie Wife, a son Buffalo Tom; By Cayuga Wife, James Jemison, a daughter; By 1st Seneca Wife, son, daughter, George; By 2nd Seneca Wife, Jacob, Goansan, Unidentified child, John Jesse.
By Hiokatoo, Mary had 6 children: John 1766-1817, Nancy 1773 or 76 - 1839; Betsey Unknown-1839; Polly bef or early 1779 - 1839; Jane 1782-1797; Jesse 1784-5 - 1812 killed by brother.
Mary's son John mar. twice and had:
By 1st Seneca Wife (dau of Georg Shongo) John, Hannah Sundowner, William, Polly; By 2nd Seneca Wife (another dau of Geo. Shongo) Sam, Unknown, Jane Jackson, Nancy Pierce.
Mary's dau Nancy mar. Bill Green and had: John Green, Margaret, Skate Green, William Green, Janet Green, Julie Green, Martha Green.
Mary's dau Betsey mar. John Green and had: Gowaneyas, Solomon Green, John Green, Daw-tah, Joseph, Lucy Sundown, Astro Thompson, SAtie Green, Mariah Green, Sarah Green, 9 others not listed!
Mary's Dau Polly mar. George Chongo/Shongo/Chango) and had: George, Seneca, Mary, James Hickie, Jackson, Cornesius and 7 others not listed.
Mary's ancestry is as follows: Father, Thomas Jemison, b. 1716, Carrickmavross, Monaghan, Ulster, IRE, d. 5 Apr 1758, Franklin Twp, Adams, PA; Mother, Jane Erwin, b. 1718, Carrickmavross, Monaghan, Ulster, IRE, d 5 Apr 1758, Franklin Twp, Adams, PA. Jane Erwin's father apparently lived in VA at the time she was killed.
Thomas and Jane had: John, abt 1739; Thomas, abt 1741; Mary b 6 Oct 1743 (supposedly aboard ship William Mary on Atlantic Ocean,) d. 19 Sep 1833, Buffalo Creek Reservation, NY; Matthew, abt 1745 Carlisle, PA, d abt 1755; Robert abt 1745 FRanklin Twp, Adams, PA, d 5 Apr 1758, FRanklin Twp, Adams, PA; Betsey abt 1741 Carrickmavross, Monaghan, Ulster, IRE, d 5 Apr 1758 Franklin Twp, Adams, PA. Another notes says there was a son George possibly raised by Indians in OK.
Sorry I can't email the tree -- my scanner won't recognize the handprinting on it.