Thanks, Thomas, for all your good information. You are correct... the census records give only very limited information about the individuals I'm looking for, so I'm focusing on other records and sources.
One interesting find is that the 1850 Census in Nelson County, Kentucky, shows a 75 year old woman named Dicy Level living with John and Martha Dykes Wagaman. She is not a parent of John, so she may be Martha's mother or other relative.
The marriage records for both Mary Dykes and Martha Dykes in Jessamine County, Kentucky, show that a Jonas Reed signed the oath of age for both girls. Further research showed that Jonas Reed was the husband of a Susan Adelia Dykes, possibly another sister of Mary and Martha. So far, I haven't found any records showing parents for any of these three women. So, on goes the search!