Some of the collateral connections are also quite interesting, e. g. the Gregorys. Fannie Marion Sims was Charles Edward Gregory's second wife (first wife seems to have died shockingly young and I have yet to find any children for her) - and he was the son of the first governor of Jersey City, NJ and one of fourteen(!) children.
I am intensely interested in the Mackey connection & already raised up Judi MCKEE on it. She has a good Geni tree of another (drum roll) Mackey family in (drumroll) Lancaster SC - and Charles doesn't fit in it. So perhaps it's a Scotland connect - I saw that Charles & Lydia Isom may have arrived about 1740.
Than for the reminder Mahala (youngest) is missing her siblings.
The main source seems to be
http://www.worldcat.org/title/mackeys-variously-spelled-and-allied-...
Hathitrust view here
http://babel.hathitrust.org/cgi/pt?id=wu.89061966214;view=1up;seq=9...
Judi McKee already combed for "named children" of Charles & Lydia.
I could swear I've seen Mackey (variously spelled) in the McElwain tree.
Now who I'm really looking for is Andrew McIlwain of Lancaster District SC, father of Mary A. Perry
http://www.nationalregister.sc.gov/lancaster/S10817729028/
And I'm trying "variously" spelled McIlwains on Geni & striking out. ? ? ?
I think we're missing more notable descendants!
From http://www.rootsweb.ancestry.com/~sclancas/records/bios/bio_drsims.htm On April 25, 1950, a historical marker was dedicated near Heath Springs in Lancaster County ... Besides the D.A.R. sponsors, there was a sizable crowd who wished to pay their respects to this remarkable man. ...
.... Also present were four descendants of Sims--Marion Sims Wyeth, Sr., architect of Palm Springs, Florida; Marion Sims Wyeth, Jr., the Macmillan Company, New York; Dr. Alice Gregory, New York City physician, and Miss Jane Marion McLean of New York City.