No, it's not incorrect nor a separate couple. They are the prince and Abel.
wait, what? ehm, does the prince suddenly change hair color...?
I thought the same. Also, neither of them look like Abel or the prince. The artwork is different too.
Abel dies and comes back to life in the body of that blonde years in the future, when the prince is already a grown man.
(⊙…⊙ )
Noooooooooooooo!!!!!
So now that we're this far in, I think it's apparent that the cover is either incorrect, or showing a separate couple. Anyone know?