Jetupset,
Unfortunately with Qantas (which is my airline's Big Brother), the staff member not the misbehaving relative gets into hot water. Banning a sibling is one thing, but I can't see anyone banning his wife.
Case in point, I recently had an FO and his wife on my flight. She was rude from the moment she boarded, but the final straw was her behaviour when I collected the rubbish prior to securing the cabin for landing.
Of the full fare paying pax, 99% put their ribbish into the supplied bags given to them with their refreshments, except the FO and his wife. Now, the FO was busy writing something (he later said it was a eulogy), but his wife was merely flicking through the Qantas magazine. Their rubbish was loosely piled up on her tray table and some of it was on the floor. Not wanting to cause a scene, I cleared their mess, and the only assistance she offered was to lift her magazine a fraction higher out of my way. She didn't even thank me when I finished. I was going to let it go, but then decided to inform them of the terms and conditions of staff travel, one of which is not to place undue demands on the operating crew's time (eg expecting the crew to clean up their mess). Her reaction was to accuse me of being rude!
Her husband apologised, and even though I felt bad for him, I reported the incident.