Benjamin ALEXANDER ws born in Richmond County, VA, about 1760. He served in the South Carolina line in the Revolution and later moved to Alabama. In closing out Benjamin's pension, Obediah and William ALEXANDER stated that they were the two sons and only children of Benjamin ALEXANDER. Obediah was born about 1783 in South Carolina. His (first) wife's name is not known. In 1830, he was enumerated as a near neigbor to Enoch RIGDON in Monroe County, Alabama. The 1840 census for Mobile County listed Obediah ALEXANDER. Also, Francis and (unk) ALEXANDER were enumerated as near neighbors in the same census. The age of (unk) ALEXANDER was listed as 90-100, making it certain that this was Benjamin, who died in Mobile in 1846. In the 1850 census for Mobile County, Obediah ALEXANDER was living with Jacob and Mary (ALEXANDER) RIGDON. Mary is assumed to be Obediah's daughter. One of Jacob's children was named Christiana. The Enoch RIGDON enumerated in the 1830 census for Monroe County, AL, was either Jacob's father or his uncle. Enoch was the son of an Enoch RIGDON who had married Sophia SHIDDLE of Lincoln County, NC. Sophia has a sister, Christiana, and the name was apparently pased down through the RIGDON line. The name Christiana is of German or Scandanavian origin, and fairly rare in American genealogical records. The geography, chronology, and naming conventions you mentioned almost certainly ties these families together. It is believed that the elder Enoch, his wife Sophia, and other family members died in the massacre at Fort Mims, Alabama in 1813.