When I was about 12 or 13, my child minder was white she had a black step daughter from a first marriage her real father had just upped and left one day, she adopted the girl , she remarried to a policeman who had his own (white) daughter, This policeman came down much harder on his black step daughter,he never really beat her,but he would raise his hand to her but never lay a finger on his own daughter who could get away with anything .
Now it's difficult to know if it was all about race as I have known some step parents be complete shyts to their step children when they are the same race,, but certainly in the english town I grew up in the racial makeup of that family was at that time rare for the area,though I can't remember ever hearing anyone make a racist comment to her and I was in her class in school,she was the only black kid in the class at school , My mother reckoned it was because she was black as I remember asking her why he was so hard on her.