Hi. I'm in the same predicament. Ping injured himself in the cage a couple months ago, so have been giving him tons of TLC in a separate cage since then. Poor baby had to wear a little cone around his head so he wouldn't chew on the stitches in his leg. He lost a lot of weight, but gaining it back. However, he was always a bit smaller than his brother, Pong. On top of it, Pong gained quite a bit of weight!
I kept Ping's temporary cage in the kitchen for a month since I had to keep a close eye on him. Once in a while, I would hold him up to Pong's cage so they could sniff each other...so they knew they were both still here. About a month ago when Ping was out of the danger zone, I placed his cage next to Pong's. They sorta ignored each other. Last week, I placed Pong in the temp cage with Ping so I could clean his cage...thought good opportunity for them to get reacquainted and keep a close eye on them. Well, they ignored each other at first, then Pong started to chase Ping and started jumping on him. Had to split them asap!
It doesn't help that Pong is now twice the size of Ping. Vet gave me recovery food to help increase Ping's weight. Any suggestions how to get Pong's weight down? =) He gets exercise and very little snacks. Anyway, at the next vet appt., I know she'll say the leg completely healed and I'll be able to put the two chins together again. Sounds like it's going to be a long process...hope they'll eventually get along again...would hate to keep two cages and not have them keep each other company.
Any other suggestions would be greatly appreciated! Thank you!!