The 1992 IGI has shows a William was a relative of William and Zilpha, with the event date as "abt. 1822" not 1820."S" describes the type of event, which means that there was some miscellanous event.
The 1992 IGI shows Thomas born to William and Zilpha in 1820.
The only son of William and Zilpha that anyone heretofore knows about was born in 1807 in the Barnwell District of South Carolina.
Wiliam and Zilpha migrated to Mississippi in about 1820.Wall was probably not maiden naome of Zilpha.The Federal goverment offered free land to descendants of a certain Indiana tribe.A the time there were unscrupulous persons who advertisd theycould trace one's family linage for a price.3 different descendants hired 3 different persons to trace her linage.The result was 3 different maiden names:Wall, Turnball, Snow.The research of some family suggests her father was William Powell, but to my knowledge, no definie link has been established.
Will you please provide us the the date and place of your William's death, name of spouse and names of children?In what county was he residing in 1850?