My mother's family included FPOC that as you mentioned appeared white and passed into white society 'but are really black whether they know it or not'. In the case of my mother's family, I have gone back to the late 18th century and found very fair skin even that far back. I can't find the African ancestor that branded them as black. for over 300 years, every male they 'married' or cohabited with has been white. I am black because my grandmother went against the family tradition and was ostracized and disowned for it. By what stretch of the immagination would this family be considered 'black', when we can't even find a black ancestor for 300 years, nor can I find a slave! If I were black with one white/Indian/Asian ancestor more than 300 years, you would laugh at me if I were to call myself white/Indian/Asian, in those circumstances.

Many of my cousins are descended from FPOC (who are not related to me)from various states. They were of varying shades of color and became free in many different ways. There are many stories of freedom out there. Some come from well documented families who have always been free, some escaped and some were manumitting, some have stories we don't know.