How can I get full custody if I've had temporary custody for a year and we have not heard from either parent since she signed temporary custody?

June 20, 2010 my nephew was born. 2 days later I went to get them to bring them home. 4 hours later I get a frantic call, the baby has cried since before we left hospital and his temp had gone up to 105. I rushed over from work to get them to bring them back to the hospital. As we are on our way she confesses that she may know whats wrong....the father was ready to leave the hospital and told the nurses that he peed & pooped when he didn't. Well his pee wasn't going all the way through. It was kind of recycling. Just never coming out. So he had to have light surgery to reroute his urinary tract. We stayed for 4 more days then I brought them home and my nephew came home with me. Then for 6 weeks we had a routine, it was supposed to be I kept him on the weekends and Mondays because I worked but somehow it got turned around and shortened. I kept him 5-6 days and she got him on Fridays & maybe Saturdays. Mom was on probation and failed her first drug test and went to jail . I kept the boy. She got out and I kept him. A year ago we told her if she wanted us to continue to take care of him we had to have some rights to him so I can put him in school and take him for doctors visits. So she signed over temporary custody. That's the last time we have heard from her. The father has not seen him in over 2 years. My nephew does not know either one of them. When she did come to sign the custody papers he was scared of her and wouldn't even look at her. This August he will start pre-k and I don't want anything to ruin his stability. We moved a year ago to a brand new home next to my husband's and my family. We are all down the same gravel road. He goes to a sitter who is a family member. And this summer I hope to put him in t-ball. What can we do to put this behind us??? Eventually we would like to adopt him. We were hoping to keep social services out if this. Our system out here is kinda messed up. Make up rules as they go type of thing. I'm just want the best for my nephew.