Narrative of the Life of Frederick Douglass written by himself is nothing less than a profound account of what the institution of slavery had upon the most intimate of human relationships. In his account Douglass gives confirmation to a great many horrors. He is the product of a white man and a black woman slave. His mother is sold off to another plantation because the wife of the white man is fully aware of her husband's behavior and this transaction was supposed to bury all evidence. As a result, Douglass was treated with much distain by those supervising the slaves, in his case his half brothers. Douglass' experience was similar to the experiences of many other slave children, however it must be noted that mulatto children were fairly common place on the plantations. In these cases the only persons who had to endure that humilitation were the wives of the plantation owners.
In the South during the time before the Civil War, any child born to a slave was a slave for life just as his or her mother was. It made no difference who the father of the child was. Even if the father was white -- in fact, even if the father of the child was the plantation's master himself -- it made no difference. The child would be a slave for life unless the master set that child free.
It was not at all uncommon for white slave owners to own children who were their own children -- ones that they had had with one of their slaves.