The Byrd Gean that married Sarah Brantley was most likely a cousin of the descendants of Bird Gean and Mourning Cates.
As to Pernecia (per her tombstone), she was the daughter of William Gean and his wife Mary Brewer (?). I have never found proof that she was a Brewer though and Pernceia's death certificate shows her as a McLoud (McLeod?). Probate records of William prove that Pernecia & Piety were his daughters.
http://www.gean-ealogy.com/genealogy/getperson.php?personID=...I am not sure if Alexander's father was an Andrews, if it was for his Uncle Lincoln Andrews, or what. His marriage certificate lists his father as Joe Marshall, dec'd. Some say Pernecia married a cousin Will Gean, but I have found no record of that, nor do I have a clue who that could even be. Who Pernecia married, if she ever married is not known to me.