How were biracial ''white'' people treated during slavery and segregation.. what happened to them?

I've been wondering about that part of history. Whatever happened to them? I'm referring to those that had a black and white parent but came out with looking white. They're not white though. They're biracial with fair skin tone.

Several likely had some African features such as super curly hair and the facial looks. Overally how they they treated? What happened to them? Or did many of them passed as Caucasians aka white passing?

How were biracial ''white'' people treated during slavery and segregation.. what happened to them?
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