Non-White love interest turns out to be White after all
A Dead Horse Trope now. Up until the 1960s onwards a common story was to have Bob, a White man, or Alice, a White woman, in Darkest Africa, Qurac, the Wild West, or the Far East, fall in love with a non-White person. The different races would be an obstacle to their happiness until it was discovered that the other partner was actually White.
Examples:The operetta The Bohemian Girl.