This should never be an issue -- I can't believe an agent gave you problems. I have a flight XXX-DCA, PHL-XXX in a couple of months. My adult son lives in PHL and will be on the same flights as mee for the PHL-XXX part. Clearly, we are on different PNRs and different itineraries, yet I called the Gold desk, asked if I could get him seats with me in the elite section, with no problem. He is not elite, and is flying on an award ticket.