proto gave great advice..its going to be tough if not impossible for him to adopt if you aren't married.
Step-parent adoptions, if you are married, are usually very streamlined, as proto said. Here, in IN, there isn't even ANYTHING, no homestudy or anything, just notification to the biodad, and that's it.
I know because my dh went through it. He was married to his exwife, and they had 2 children together.....she also had one from a prior partner....but my dh raised that boy as his own as well....they always planned to have dh adopt the boy, but well..they divorced...halfway through the divorce, the lawyers told them the adoption wouldnt happen if they werent married, so they had to DROP the divorce proceedings, do the adoption, then refile for divorce.