Theo, Alias, and Norma spent their most time ever together in the same room- probably around 15 minutes. Theo now is curious enough to sniff his siblings. I have found one successful thing is to hold either Norma or Alias as Theo is checking out the other sibling. This way he doesn’t feel ganged up on. His hissing was minimal, but when he does, poor Norma in particular looks offended. Hopefully soon, all doors will be open to all housemates.