Bewley Family Tree

PLEASE HELP!!!!! I have recently started to search online for my family and have been somewhat successful with finding out where they were.

I know that my great great grandmother Nancy Johnson Bewley (b.1891-d.1989) married my great great grandfather Hubert R. Bewley. My great great grandfather Hubert is the son of Tom and Nishi Hall Bewley. Unfortunately, I do not have a name for Tom's parents but that he had two siblings Charles and Vina Mae. I only have a first name for Nishi's mother (Betsy).

My great great grandmother Nancy Johnson Bewley is the daughter of Richard and Sally Allen Johnson (b.1852-d.1953). I have no names again for Richard's parents but do have his siblings as Toby and Ed Johnson. In addtion Sally's parents were John and Sarah Allen.

Right now I have no idea where I should start. I have been told that there is a way to look up slave records to find out where they were born but I really have no clue. If someone could please help point me in the right direction to find these documents I would so gratefully appreciate it.