I met a lady, whose job was to meet with Perverts in the jails and such. She told me, once a pervert, always a pervert. She said, in her job, she has had many letters given to her from these perverts, that they had seen the "light of God" and blah, blah, blah therefore please let me out of jail, let me go back to my job that I had and let someone watch over me with the kids and such.
As a Catholic, we know that IF, one goes to confession and is sorrowful, sins are forgiven, BUT, in my opinion, I would be very careful around someone like this, for yes, they could go back, just like an alcoholic. And the Catholic Church had a group of the Sacred Heart for those with addictions. To be a member, you had to follow the rules, and those rules were to receive the sacraments as often as possible and etc.
I too, would not see to marriage for this person, and blood tests are an absolute! I would think that taking care of ones self would be enough cross to bear. How about those who are bisɛҳuąƖ? In my sister's case, the marriage was invalid, for he lied, kept a secret. Now my sister with 2 sons, has genital herpes.
Some sins, I think are harder to deal with.