It's true that KL's hair seems to be more blond, that's why I have doubts on this identification.
And this "19th century Habsburg type" is so strong, especially when they are young, that it's sometimes difficult to recognize somebody between all these guys with this long face, domed forehead, big lips...
If not KL, I think it's a member of the branch of Toscany...
(But look how Maria-Annunziata, KL's daughter, has got a striking ressemblance with your portrait... Even if it doesn't mean anything, as I said, all the Habsburgs had this face...)