I moved back into my parents house almost a year ago. They have one kitty who's a 16 yr old female (Birdie). I brought my two with me (both girls)aged 5(zelda) and 2(cherny). Ever since I moved back they attack the 16 yr old constantly. At first, I chalked it up to territorial issues...but it's still happening. The 2 year old especially seeks out my elder kitty to attack her. Shes done it while Birdie was going to the bathroom, sleeping etc. Ive had to set up Birdie in my room with food, water, and litter box because she's gotten really scared and stressed from it. I have to escort her around the house just to make sure she isnt bothered. Birdie hasnt done anything to provoke them and goes out of her way to avoid/keep a low profile. I'd really like some help because I'm worried its going to affect her health. Also, they are all spayed. Any input would be appreciated!!