Definition: Given a real-life anecdote of a complex ethical situation, generate a suitable title that describes the main event/root cause of the situation. Imagine that the given text is a social media post, and you have to write the title of the post, so the users can decide to read the main text or not.
Input: My sister and I both live at home, with our parents. I've never left the nest, and while she has (She's 5 years older than me, and had a bit of a head start), she moved back in maybe 2 years ago after spending a few years living with her former boyfriend. 


Now, my whole family has always had cats. Sometimes a lot of them, even. When she moved away, we had five-- she took two with her, since there was one she actively wanted to take, and the second was bonded to her, and the only cat that tolerated being around the one she actively wanted. Over the time she was gone, the bonded one died, so she moved back in with the remaining one. And here is where our issue kind of started.


Over the time she'd been gone (maybe about 3 years), the three cats we had left may have forgotten the one she took. But, being older cats, used to each other, they didn't take kindly to a 'new' cat returning to the roost. So, for a little while, we sequestered my sister's cat. It was to be kept in her room with the door closed, to give it a safe place to not be attacked or worried about anything. Things were okay for a bit, and we were slowly trying to warm them up to each other, and eventually let my sister's cat back out into the house at large. But, one of the older cats started getting really territorial and aggressive at this point. She stopped using the litter box, and began destroying things in the way cats seem uniquely well suited to do. It was... Bad. We isolated that cat, tried different brands of food, of litter to try and attract her back to the box, literally giving her prescription pills to try and relax her after multiple visits to the vet. We spent almost a year and a half trying to fix things before the cat was finally put down (Sheltering wasn't an option in our area, and nobody was willing to foster a territorial cat that was using the toilet everywhere she pleased). Barely a month later, the second of the older cats got very sick, and passed away naturally.


I'll break the narrative here to interject that, while this was going on, my sister decided to adopt another cat. You'd think this would be a bad idea. ... I SAID it was a bad idea. But my mother is a pushover for cute animals, even if she is the one most in favor of putting them down if they become a problem. So, my sister begged and twisted her arm until my mother let her adopt a second cat. So at that point, we were back at 5 cats. Two living in my sister's room until they got more acclimated, three living in the house proper. None really happy to interact with each other, and one actively throwing a rebellion against other cats existing. Upon recognizing that adding unfamiliar cats to the environment had thrown things out of whack and made things unsustainable, my sister consented to keeping hers isolated again, to try and fool the old cats into thinking the new ones were gone.


Fast forwarding back to near-present. With two out of three older cats now gone, we're down to three total again: My one cat, who we've had for about 13 years. She is very small for an adult cat (think 'runt of the litter'), who has never been confined. She has full access to the house, except my sister's room. And opposite her, my sister's two cats. Both of them are younger cats; one is maybe 8 years old and pretty chill, albeit a bit territorial. Doesn't really seek out trouble, but will give you some if you come looking. The second is only about 3 or 4 years old, but really physically large. Given she's pretty young, she's still very energetic and playful, and constantly tries to escape my sister's room. Given she's got two cats isolated in her room, and one actively wants to get out and roam, my sister wants to let her cats out.


Now... This is where I specifically have an issue. My cat doesn't like the other two, but when they are out, will usually just sit with me and growl for hours on end, until she forgets they exist. The cat is usually glued to me anyway, granted. My sister's younger cat, however, likes to play and explore. Her idea of playing happens to include stalking my growling, openly hostile cat, and trying to pounce on and attack her. The younger cat goes so far as to hide under my bed and wait for my cat to jump down, so she can go to town on her. This isn't a new or unfamiliar trait, and this kind of interaction is part of why we kept them separated to start with-- just today, I got a big cut on my foot because my cat was sitting on the floor next to me, when the younger cat brought the beat-down onto her(And by extension, me).


After a lot of scrambling to separate them, my sister sent hers back to her room, while being kind of sulky and passive aggressive about it. I feel like I'm being made to be the bad guy here-- and I can kind of understand why, since I have one small cat that lives in an entire house, versus her two that are isolated to a single room, that my sister also feels isolated to. But I don't think it's fair to restrict my cat now that she's in the minority, because of decisions my sister made. And likewise (apart from me getting hurt as collateral damage), I'm honestly scared of leaving my cat alone in the house with hers during the week, with everyone in the house working full time jobs. I don't want my cat to get hurt or attacked when I'm not around to break up a fight and protect her. Even if the younger cat thinks of it as playing, I've got enough cuts to know that at least one of them has claws out for it, and I don't want my cat in a much lower weight-class to be getting into fights she can't be helped out of. ... And that's not even touching on the mismatch between her cats needing to be on a diet, versus my cat having food constantly out to *encourage* her to eat, due to being so small and thin.


TL;DR: I don't want my sister letting her two recently introduced cats out of her room, for the safety and well being of my cat that is older and smaller, and was here first. I don't want to tell her to wait for my cat to pass away before hers can be allowed to roam the house, but that feels at the end of the day what I'm asking for. AITA here?

keeping my sister's two cats locked up, while my one freely roams the house