The more important questions are:
Is he a sex offender with children? Has he been proven a danger to CHILDREN?
Or is his status based on crimes with an adult?
If it is based on improper behavior with an adult it doesn't necessarily mean he will lose custodial rights.
I have seen it happen -- a sex offender in my neighborhood lives with his wife and children. They are trying to evict him because he also lives in the vicinity of the school and claim he is a danger to children yet haven't tried to remove his children from the house because he is not a danger to them and is a fit parent. (Yes IAAL I know that doesn't necessarily make sense but Ohio is definitely a DUFUS state in many regards.)
So who were his crimes against? Was he a sex offender when you decided to have a baby with him.
How old was he when he had sex with this "minor child", and how old was the "child"??
Do you really believe he is a danger to your child, or are you just grasping at straws to keep him from your child? Children do deserve to have both of their parents...hopefully you aren't grasping at straws