Paternity must be established before any rights can be asserted. In a Court case you either stipulate to paternity or dispute it and take a DNA test. You seem convinced he is the childs father. Your comments do not include what level of involvement he wants. If he is demanding to take the child on visits, then the child's welfare is endangered because 1. the boy doesn't know his father,2.father is an alcoholic,3.Father is probably clueless as to the need for car seats etc.
THe short answer to your question is yes it has happened that even father's with a criminal record and alcohol addiction have earned there way back into their children's lives. BUT they have to work for it. Therapy,supervised visitation,drug rehab,a stable home enviornment, a job, pay child support etc. in your case he has even a harder road to redemption. He raped an underaged girl and is a sex offender. I doubt that even with all the good deeds that I listed that he would get more than supervised visitation.
You should go to Court and get an order that you have sole legal and physical custody, ask for child support and request that the Court supervise visits. Make it a Court order, if he harasses you, get a restraining order. In short take all steps necessary to protect your child.
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