If they are already in state care, you absolutely positively must have CPS/state involvement if you are going to keep these children for any period of time longer than an afternoon babysitting gig on weekdays.
This isn't always the case (at least in my state), but it definitely requires a lawyer who is very knowledgeable of the juvenile court system and various avenues for guardianship, temporary custody, etc. Also, doing this typically pisses CPS off, but sometimes that is necessary.
I will update tomorrow after I talk to everyone suggested. I will do absolutely anything in my power to get these girls placed with me. Their lives have been so unstable, and I could provide them with security until I am not needed, and hopefully far beyond that time.
What you will want is an attorney who handles Third-Party Custody (non-relative caregiver.) You will definitely want papers. The schools won't let you enroll, you'll have difficulty getting medical care, all sorts of obstacles without letters of authority. There are differences between guardianship (which I had with GD1 when she first came to us) and custody (which we have now via DSHS/CPS). If they are in state custody, call the caseworker and offer your home as a "friend-of-the-family" placement; with FOF designation you could be considered a "relative" caregiver. You will probably have to go through licensing, or at least some of the qualifications for licensing, which is a PITA but definitely do-able. If the parents rights are terminated, they will become legally free which at some point the state will look to adoption for the children, whether that be you or someone else. (Just so you can make sure you know what you're getting into; the end result will be either resolution and reunification or non-resolution and termination, they don't like the kids to linger in the system for too long anymore.)
Let me know if you have any questions. I had guardianship in Ohio for several years and am dealing with CPS in Washington for several more, culminating in termination of parental rights and adoption. I can't give legal advice or tell you what to do, obviously, but I can give you an idea of what I've gone through (both in the caregiving and in the parent's gamesmanship and battles to get the daughter/s back.)
Thank you for this information. I would not hesitate to adopt them if it comes to that. And I have issue getting licensing or anything I need to do to help these girls. I do know both parents and all grandparents are supportive of me taking the girls, so maybe that will help sway things in my favor.