Let me start by saying I didnt exactly impose an ultimatum or anything like that. Those are automatically YTA material. 

Now she has always loved animals, which I get and I love them to, but not to the extent which she does. Animals are a lot of work and a lot of money to take care of between the food, the litter, (for cats which is what we have) replacing the litter boxes every so often, etc... Well when we first got together she had 2 cats. Fine and dandy, 2 is manageable and I like cats so no big deal. Well after picking up a few strays along the way, and not having the money to get them fixed when we should have (don't start about that, I get it, bad cat owners. Remember what I said about them being expensive?) we eventually topped off at 6 permanent cats with litters of kittens that we got rid of along the way. It hasn't been easy and its caused a lot of stress between us and to us personally but we made it through. Last year we lost two of our cats due to health complications (we got them to the vet, they were sick with feline leukemia and we had to have them euthanized for different reasons between the two of them). It was very hard on both of us but we were back down to a manageable, albeit not ideal, 4 cats. Well guess what? The only female kitten we have got pregnant again and had a litter of 5 kitten, we still have all 5 6 months later with no end in sight. Oh, and guess what? She's pregnant again and about to burst. Our last male cat has an appointment to be fixed this month and I told her outright that if he doesnt get fixed, and the kittens that are 6 months old aren't gone by the end of the month, I'm leaving. 

Now let me explain why, besides the ridiculous amount of stress it puts on me since I'm currently staying home and have to clean up after 9 cats, and stay up all night to make sure the kittens don't end up pregnant. When our pregnant cat has kittens again, I can see her current kittens causing issues for the new litter. The current litter likes to try to be around mom, obviously, but the mom doesnt like it, I guess because she's pregnant again. So I can see that being a problem when mom is with her new litter. I also am fearful for the health of not only our cats, but the 6-month old litter. Feline leukemia is contagious and we aren't yet sure which of our cats, if any more, have it. The longer this litter is around our cats, the more susceptible they are to the disease. Also the 6-month old litter is causing a lot of stress to our current cats, cause we simply dont have room for 9 cats plus ANOTHER litter right now. 

I'm at the end of my rope. She won't meet me halfway when it comes to getting rid of them. The animal shelter is very expensive to surrender them to ($100 per kitten) amd she doesnt want to post them online because she wants to make sure they go to a good home, which I understand but look what that's costing us. I left home almost a week ago to get a break from all the cats and if it were up to me I wouldnt go back, but I wanted to make it clear to her that I absolutely would be leaving again for good if the kittens weren't gone by the end of the month and our last male cat wasn't fixed. AITA here? 