The bio dad's SO is white.

Both bio parents are black. Both stepparents are white. Clear?

It's probably a generational thing...when I turned 14 it was the time of X clan and malcolm x hats. Alot of black kids i grew up with became involved with black nationalism and as a result, stopped hanging out with white friends. One friend in particular had a white stepfather. He started rejecting him in various ways....one of those ways is that he stopped calling him dad and started calling him by his first name. They reconciled years later but he continued calling him by his first name. This memory crossed my mind when considering my current situation. It's the one way that race might play a part in how things turn out. I probably wasn't clear enough when alluding to it.