My sons biological father has been in prison from ages 0-1, 2-4, 5 till current. Since the age of 5 I have been with my fiancée and we are getting married this year. We have 2 children together. Can my soon to be husband adopt my son without having his biological father having a say? He writes my son every 6 months and I have encouraged my son (12 yr old) to write back but he doesn't want to. I have concerns that if something were to happen to me, would my son get caught up in legal issues if his biological dad gets out soon.

What is the best way to go about havign him adopted legally by the man that provides for him?

First you have to get married and be in a stable relationship for a year or more.

The easy way is for the bio father to agree to the adoption. If he does not/will not, then you can go to Court and attempt to force him to relinquish his rights. You probably won't be successful because the Courts are very reluctant to remove blood ties.

You can't claim that the father is ignoring the son if he writes letters.

And if the father wants to pursue visitation you will have to counter with your feelings that he is a bad influence and a danger to your son.