Can I get custody if my son back after 13 years?

I was pregnant with my son when my children were removed from the home after my sister (15 years) left them alone. I was put in a pre-trial detention program and successfully got all my kids back. However, I made an emotional decision to let my son stay with his aunt because he'd been there since birth. His aunt pleaded with me to allow him to stay and we would share custody. Over the years, he has gone back and forth visiting with me but I do pay child support since I'm the noncustodial parent. His older sister died last year and before she died, we both talked about making our family whole. Now, I can no longer consider how his aunt may feel regarding him leaving to stay with me. My son (13 years old) has expressed interest in wanting to live with me but doesn't want to hurt his aunt. How do I go about obtaining custody of my son or do I still have it?