The prince's lineage checks, of course, as royalty. That's why he's a prince.
His fiancee's "white" lineage also checks, according to Wikipedia, as being at least partly descended from royalty. His brother's wife is, similarly, also partly descended from "white" royalty.
Has the royal fiancee's "black" lineage has been checked for royal descent? Again according to Wikipedia, African nations had kings, queens, chieftains and tribal leaders.
In these days of DNA testing, why not have a look?
(Unless being attractive and born in Southern California trumps royalty.)
...Wikipedia lists "Zulu Kings" as its own article. African nations had regional, royal lineage. Not a joke.
Kings and sons of kings are listed in the article, and it appears that the term "ka" is given to the sons recognized within the Zulu royal lineage. This is a term we, in the present day, sometimes associate with spiritual beliefs from Egyptian antiquity.
Meghan Markle, part 4 Ancestry at Wikipedia
Catherine, Duchess of Cambridge, part 6 Ancestry at Wikipedia
List of Zulu kings at Wikipedia