I had two Robo sisters for a while, until one escaped at night and died by accident (long story!), so we went back to where we got the girls from and we got another two of my ones sisters. They were fine but one seemed a little off and unfortunately died in the night. Her sisters never touched her though, they didn't want to be near her.

The thing with rodents is that most will pick on one that isn't doing too good or has something wrong with it (thats still healthy though) because they know its "different". My gf had this problem with two female rats who were sisters. One was blind and deaf and the other would pick on her a lot, so they had to be seperated.

For them, its life. Its instincts and you can't take that away from them. For us, its weird and upsetting