He is doing exactly what you think he is.
He is "dissing" you big time. What you see is not really jealousy. He is pulling rank on his subordinant. He is demanding that you pet HIM, not the subordinant dog.
If this were my dog I would handle it just like another dog handles this kind of disrespect.
It would be quick, loud, and effective.
As soon as I had the desired "startle" response from the impudent one, I would give a command, (sit or down), and reward the dog.
running 2 dogs of the same sex, esp when one is a working breed like a Dane, can be difficult. If you have not neutered both of them already, I would highly recommend that be put at the top of your priority list.
Otherwise, you are doing a great job, keep reinforcing the dane's position, but he needs to understand he must respect you as well.
