The reaction is understandable. Since the trans-Atlantic slave trade and colonialism created the idea of a single African race, the term “black princess” has been an oxymoron. The conception of black womanhood that scholars frequently cite — mammy, jezebel or sapphire — is antithetical to the idea of a princess, a cosseted women whose prince comes to sweep her off her feet and solve all of her troubles.

In fact, black women have become royals for years and years, unbeknown to many.

Some aristocratic families in Europe have already broadened the idea of what sort of spouse is acceptable, said Archduke Franz Ferdinand von Habsburg-Lothringen, whose great-great-great-grandfather was Emperor Franz Joseph I of Austria, king of Hungary. His wife, Archduchess Lei von Habsburg-Lothringen, is an African-American lawyer who grew up in the traditionally black New York City neighborhood of Bedford-Stuyvesant and in Columbia, S.C.

“For the modern Habsburgs,” Mr. von Habsburg said in a telephone interview, “the importance of who your wife is is more about whom you have fallen in love with than how they fit into the aristocratic family.” That he is an archduke rather than a count reflects his family’s shift. In the past, he would have lost his title for his marriage, but now he and his wife have kept it and are presented in family gatherings as such. “The family modernized its rules to survive,” he added.

Image Prince Maximilian of Liechtenstein and his bride, the fashion designer Angela Gisela Brown, at their wedding at the Church of St. Vincent Ferrer in New York in 2000. Credit... Stephen Chernin/Associated Press

He and Ms. von Habsburg are not the only mixed-race couple. Mr. von Habsburg’s brother married a South Sudanese woman, and other European royals with black spouses include Prince Maximilian of Liechtenstein, whose wife, Angela Gisela Brown, is an Afro-Panamanian from New York City, and Christian Louis, Baron de Massy of Monaco, who married a Guadeloupian.