My sister passed away in May of this year and I was wondering how long it would take to adopt them, or even if I had the right to adopt them. 2 were results of rape, while the oldest's father isn't in the picture, and by all appearances doesn't want to be either.

I cannot see where you would not have any particular right to adopt your nieces. The court may look favorably on you, being the maternal aunt. You need to find an attorney who works in adoption law. File a petition with the court. The two girls will be assigned a court visitor and also a guardian ad liteum - that is to protect their interest and make sure that you are the best choice. You pay for that, either in your attorney bill or separately. If you pay them separately, they will each send you a bill. Your home will be visited by the county, you will have a home inspection by the fire department, you may also be required to attend a counseling session as well as take a MMPI - a personality inventory test. When all that is done and the court has the documents, you will have a date assigned for the adoption hearing.

I cannot tell you how much it costs - it is going to vary. My youngest is adopted and the total cost of everything came to almost $1400.00. You may also have different requirements. I am only telling you what my (now ex) husband and I had to do, according to our state laws. It is best that you contact an attorney where you live, contact Social Services (are the girls in foster care now?), talk to their Social Worker and explain your desire to adopt. You may be given good advice there and recommendations.

Wishing you the very best.

My sister passed away in May of this year and I was wondering how long it would take to adopt them, or even if I had the right to adopt them. 2 were results of rape, while the oldest's father isn't in the picture, and by all appearances doesn't want to be either.
No... the girls and boy are in my care... put there by CPS... would legal guardianship be the better option?

You adopt them, that is how I would do it. But ask an attorney. He would know which route is best for you. Much good luck!