AITA for helping my sister leave our parents house and doing nothing for my much younger siblings?

My parents had me (19m) and my sister (18f) when they were 20/21 (me) and 21/22 (my sister). They never really parented us. Most times we were left home alone when we were way too young. We had to learn to fend for ourselves. We missed a lot of school and didn't always look taken care of either, but we didn't have extended family around us and our parents never had friends at the house either so we were pretty isolated and ignored. I was 8 when I started attending school regularly and my sister was 7. And that was because our parents got in some trouble and so they told us we were big enough to get ourselves up and to school every morning. It wasn't easy and the two of us bonded over the unfairness.

Then when I was 11 and my sister 10, our parents had another baby together. This was the start of them pushing out kids like crazy. They had five kids in seven years and my sister and I were forced to be responsible for them. Our parents were home more with those kids but they did nothing. They were too busy making more kids to raise the ones they had. During mom's pregnancies we were also expected to wait on her and that sucked.

Our parents made life really difficult if we tried to stop. I spoke to teachers and CPS called a few times but nothing was ever done to help us. So I left on my 18th birthday, slept rough for a few weeks, was able to get help at a shelter and got a job and found a place to rent. I kept in touch with my sister and we planned for her to come and live with me when she turned 18. She turned 18 in December and she moved straight in with me. I told her she should try to finish school since I didn't. There was no point. My grades sucked. I'm working to support us and she's got a part time job now so she can help and we're going to make it work together.

Our parents tried to report my sister missing and created a huge fuss over her leaving. When we found out she corrected it but that gave our parents more current info on us. They found out where we live (at least the neighborhood) and I see them when I have to walk to work. They told me I should be ashamed for moving my sister out like I did and they asked what about the younger kids and who's supposed to take care of them. I said they had them so they should take care of them and they said I know they won't and we left little ones with nobody. My mom's pregnant again and probably due any time now from looking at her so there's even more kids than before.

I know my parents won't take care of any of them. I know that I should probably step up more. But I never felt close to them. I took care of them because I had to, had to parent out of force but I never loved them or did it because I was willing. And I don't want to be responsible for them again. My sister feels the same and she told me she called CPS and reported it but that's all she's willing to do and she's done with it because she wants to focus on the two of us.

AITA for doing all this for her and not doing enough for them?