I mostly agree with SuperCuteRainbowPets. Youll want to keep them completely separate, but only for a few months. Keep their cages a few inches apart, but close enough that they can see and smell one another. Alternate their play time in another area, so they cant nip the other bunny through the bars while they are out. Keep them like this for atleast two months, then try again with a similar but different tactic. Get a box thats big enough they can both lay down, but thats it. Put them in the box in a neutral room for two minutes and pet them the entire time. Put them back. An hour later, do the same thing. Do this a few times for a few days, then start with longer sessions in the box where you watch them the entire time, but dont pet them the entire time. If they can handle that, try bonding in the tub or kitchen again with a ton of short sessions spanning to a few long sessions. If they cant handle this for whatever reason, then it sounds like they just dont get along