Duke of Wellington's great granddaughters (he's over 90). The nieces of Lady Jane Wellesley. Posted about this a week ago. Good option
Ah. I wasn't on the board a week ago and haven't read a lot of the pages for this thread yet (there's a lot!). I had a moment of "there's a few dukes out there still..."
I'm not sure which great granddaughters you're referring to. My knowledge of the current Duke of Wellington is, sadly, lacking, but based on his Wikipedia page I see he has 5 children; Charles (b. 1945), Richard (b. 1949), Jane (b. 1951), and James (b. 1964). Charles has 5 children, born between 1978 and 1990 (and presumably his daughters, Mary Luise (b. 1986) and Charlotte Anne (b. 1990) could be a match for Harry), and 4 grandchildren, born between 2005 and 2010. Richard also has 2 daughters, Davinia and Natasha born in 1977 and 1981, John has a son (b. 1981)and a daughter (Alexandrina Sofia, b. 1983), while James has a daughter born in 1995.
Of the bunch, Mary Luise, Charlotte Anne, Davinia, Natasha, and Alexandrina (the current Duke's granddaughters) are all of an eligible age for Harry (although I'm unaware of whether any are single or not), although I would think the current Duke's great-granddaughters would be a tad young.