How do I go about getting sole custody?

[Janet Pierce]

Amid has things a little jumbled up. This info is for the whole US (and several other countries).

Currently mom has sole legal and physical custody and you have nothing. You don't even have a child yet. Only YOU can sign your name to the AOP, mom couldn't if she wanted.

You need to file a petition for a paternity action where the baby lives. You request court-ordered DNA so it's legit. If it comes back as you then you file for visitation/custody. I will tell you right now that you will NOT get sole custody nor with you get physical custody. Because unless mom shows up to court with baby on one arm and a needle sticking out of the other she will not be deemed unfit.

You will get graduated visitation, allowing you longer and longer visits. And she will request (and get) child support.

Unless her other child was taken by child services, where that child lives is irrelevant. As the custodial parent, mom gets to determine WHERE the child lives.