Birds most DEFINITELY feel jealousy! It's often a huge problem in over bonded birds that are naturally pair-bond birds in the wild. My conure, for example, has exhibited extreme jealousy issues in the past. Thankfully we've worked past most of them, and as a result she is no longer a shoulder bird in my household. My IRN also shows jealousy issues, but not regarding human-to-human interaction.
Birds will often work out their own hierarchies, but if you feel that one bird is a danger to the other, do not let them out together unsupervised. You will have to work with each bird to create a neutral environment where neither feels they are "king of the castle". There's no guarantee they will ever become friends, and no guarantee that they will not. By the sounds of it, your OWA does not enjoy having someone coming into his territory and interacting with his mate.
I'm hoping that someone who was large-bird experience will help you out more with jealousy issues with these two. Unfortunately I only know of what it's like between two small birds, and because of their size they are very easy to manage.
Either way, congratulations on your new addition!
