we have 2 cats,3 yr.old siblings.we recently adopted 2 new cats,found as strays by the spca.they are toms,neutered late in life (estimated they are 4 to 5 yrs old)but they are very good with each other(usually)and especially good with people.we kept them in a bathroom "safe" room for 2 weeks.we traded blankets and toys between the original and new cats,so they could be aware of each others presence.yesterday,we had what was meant as a brief supervised visit.it went so well,we felt comfortable leaving them together in the living room all night.at 6 am,i was awakened.the 2 new cats were hissing,growling at each other! i immediately removed them to their safe room,where they calmed down at once and recognised each other as friends again.they are now napping peacefully.WHERE DO WE GO FROM HERE? the 2 new ones seem very at ease and content and harmonious in the safe room,but its a bathroom after all and i cant let them live in such a small room forever,that would be cruel.what do i do now?and why would they suddenly get mad at each other? any advice or guideline gratefully appreciated.btw,all 4 cats have felv.i voluntarily took on the first 2 to save asymptomatic cats from being euthanised,and they have been such a joy that when i heard about the other 2,i decided to give them a home as well.all 4 are doing well at the moment,so keeping stress minimal is important in their treatment.so,this is an especially delicate introduction.