I know he couldn’t have ‘married’, per se, but imagine. Would the husband be Duke of somewhere else, or would they both be Duke of Cambridge?
Also what title will Harry have if he marries?
As William would have been Duke the same sex civil partner (perfectly legal and of equal standing under UK law to marriage) would most likely (if the Queen decided he should be so titled) have been either Viscount or Baron as these are lower than Duke in the order of chivelry.
The Male version of any ‘level’ ranks higher than the female (I know it’s sexist but there you go) so King out ranks Queen and Duke out ranks Dutchess.
As for Harry his title when he marries is up to the Queen as they are in her personal gift.
that would be his title
he would have no title at all b/c it’s illegal