I do not think dogs get "jealous" -- that is a human emotion. I do believe that dogs understand possession, and what we see as evidence of jealousy may indeed be nothing more than a dog asserting his/her rights over his/her possession -- the owner. Since it is not a great idea for a dog to think the owner is his/her possession, such behavior is best discouraged rather than reinforced ("oh it's okay, I still love you" followed by lots of petting is reinforcement). When I have had dogs do this type of thing, I ignore the pushy, possessive one as a way to indicate that such behavior will not be tolerated and does not result in regaining the possession (me, my attention) while continuing to pay attention to the other dog(s). A friend with a very possessive poodle simply puts in her another room behind a gate when she growls when the other dog is receiving attention. They get the message pretty fast.
Mary-Ann Bowman Emma, Abra, Maize and the ten-pack