You have quite the tangled web here, and it's unlikely you're going to be able to resolve it satisfactorily, unless there is award space available, or you can beg the airlines into opening it. You then cancel "Jane's" award tickets and book a new award for Traveler #5 - though, admittedly, that's a super long shot. You don't say it explicitly, but since "Jane" seems to have been traveling with a minor, you now seem to have a pseudo-unaccompanied-minor situation where nobody else is on the child's PNR, and the child is flying alone in J -- which, honestly, I have no idea how Cathay or Etihad will react to. That would seem, to me, to be the bigger problem than how to get "Traveler #5 " onto the itinerary... If the child were 12+, maybe no big deal... but at age 3, I think you're treading on thin ice. They may deny boarding on that one without an adult in at least the same class of service.