Quoted from SilverUnicorn:
Thanks for the well wishes! Hobbes is NOT getting along with his brother AT ALL. They really got into it tonight. It's like they never knew each other. More stresses. Keeping them separated and trying to do scent swaps to get them acclimated again.
That's typical after an extended vet visit. One cat doesnt recognize the others scent. It will get better shortly once that nasty vet smell wears off