I found this family tree of the Jemison's online. It matches up with my family line to Mary Jemison although some of the dates are incorrect. I've run across some of the same incorrect dates doing research so if you are going to use it, I'd recommend still doing the research but at least it can provide some clues if you are stuck. It provides a lot of great detail into the descendants of Thomas Jemison.
http://familytreemaker.genealogy.com/users/g/o/d/Alexis-M-Go...