Sudden Aggression in 2 Yr. Litter Mates
I have two identical twin male cats. They're 2 yrs old and both fixed. I adopted them from the Humane Society when they were between 6-8 weeks old. They've been raised together, never been separated and have always gotten along. They've always played together, bathed each other and aside from some rough play when much younger have never had a problem. Nothing in my life has changed, no furniture moved, new people, visits to vets, medications, etc.
I woke up 2 days ago to a living nightmare. They are completely at war. They can't be in the same room without going for each other's throats (seriously) I finally figured which was the aggressor, the calmest brother. Their fur blows up from head to tail, snarl, growl scream,hiss and attack. The other one hides under the bed in a defensive posture, teeth drawn, snarling, etc. I've separated them - not easy in a condo-ever since.
My question is: What can explain this bizarre behavior between litter mates who have always been together & happy? I'm a single "parent" and always try to give equal love.