...of older rabbits that have been living separately to bond?
You see, my two buns are brothers and used to be bonded. We did a big boo-boo when they were younger, and when Dylan was beginning to have his teeth problems, we only took him, and not Thomas, to the vet. Eventually, they started fighting.
We didn't really have much time (should've made time, really) and so, we never really re-bonded them together. Over the years, their hutch has been together (through wire) and they can even reach each other. They tend to groom one another through it. Never fought.
HOWEVER. If you release the two, they always fight. They'll tolerate both being out at the same time, but NOT being in each other's eyesight. Or their favourite area of the house.
We tried for a bit when we moved, and they didn't seem THAT bad. But they still fought when together.
I think they're 6 years now, is it too late...?