I think perhaps your brother should contact her and say that Nyarly is not adapting well to the other cats and that some decisions have to be made - either the shelter or re-homing him. If she has no one else to rehome him with, I hope you folks know someone. Is your shelter a no-kill?

If after getting that message she doesn't respond - maybe give her a deadline of a week or whatever - then rehome the poor baby. He deserves a quite and loving home and so do you!