Taking Social Services to court for custody?

Well I am a foster parent and I have had these children in my care for 5 years so they look up to me as their parent. The case is currently in permanency but were recently removed from my care because the worker has something against me and my family. I have brought this to the director and nothing was done. I saw the children once since the removal and all they did was cry to come home to me and wouldn’t let go of me. I also asked the social worker I want to go for custody and then that’s when all these accusations start coming up. I’ve taken this removal very hard because I had the children for a very long time and I had the youngest since he was 1 years and the girl since she was 4 and the boy when he was 7. The children know they have biological parents as I told them and I agreed to start having visitations at the county office to get to know her but she keeps falling off the wagon and going back to drugs. Anywho I was asking can I take the social services to court for a custody battle? I’ve been told we can and the children were in my home more than 6 months(more like 5 years) I have proof of what the children told me while they had visits with their mother and what she said and I have audio and I am very close with the family and they’re on my side and want me to get custody of the children. I know this a dumb question but I dearly miss the children and want them back in my care permanently. Please NO smart remarks thank you.