I live in the state of Indiana.
Circumstances:
Engaged mother of a 3month old boy.
I am 21 years old, fiancé is 20years old.
Biological father of my son is NOT on the birth certificate. He is currently engaged and has 4 other children. He wants to sever all legal obligations and rights to my son. In turn my fiancé wants to adopt my son. What steps do I take ?

Find an retain a Family Law attorney. I would not consider doing a step parent adoption without one. The fact that the father is willing to sign over his rights is a plus, the fact that he is not on the birth certificate is a minus. The court hearing the adoption petition will require that the father be identified and his permission for the adoption obtained. But because he's not on the birth certificate that will mean he will be required to acknowledge paternity to a DNA test will need to confirm paternity. An attorney can advise you on the best way to handle this.

You will probably have to wait until you are married at least a year to submit the petition.

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You will probably have to wait until you are married at least a year to submit the petition.

Maybe. Maybe not. It varies from state to state. But you will have to be married first.