Usually princes (the children of Kings and Queens) have dynastic titles granted by the king or queen. This allows them to own landsand have power, authority, and governing rights (otherwise a prince would just be a freeloader with an empty title). An example is the British royal family. Prince Harry IS a prince because he's the grandson of the Queen, but his actual official title is Duke of Sussex. Prince William's title is Duke of Cambridge.
That's why British people will often correct people when they call William and Harry's wives as Princess Kate or Princess Meaghan. Prince Harry and Prince William are referred to princes because they're of the royal bloodline but their
OFFICIAL titles are DUKES and not prince, so their wives are Duchesses.
Ohhhhhhh, I see. I usually see only the princes who aren't the crown princes being given titles like Duke or Count for the not being a freeloader prince reason in manhwas/mangas and that the crown princes' only title is basically just prince since they're succeeding the throne. This is interesting, thank you!
wait how can she be duchess and crown princess at the same time? does the ml hold a duke title?