If you are not the child's biological father, but you and your wife were married when the child was born, and you signed the child's birth certificate, you are the child's father, regardless of anything else -- and, more importantly, you are the only father this child has ever known, and it would no doubt cause the child serious damage if you tried to deny that you were his/her father.
If the mother has sent the child to live with you because mother cannot handle the child, you already have full legal and physical custody of the child, and this should have been dealt with at the time of your divorce, so that is a bit confusing.
You should consult with an experienced family law attorney in the county -- Hampden -- where you reside to discuss more specifics of your case, and how to go about obtaining (in a court order/judgment) sole legal and physical custody of the child, and for child support from mother to be paid.
Best wishes to you and your family.
No attorney-client relatonship is created in responding to this question, and advice provided is based solely on very limited facts presented, and therefore may not be correct. You are advised that it is always best to contact a competent and experienced with the practice of law in the county in which you reside, particularly as it relates to family law, child support, custody and visitation (a/k/a "parenting time") issues, including 209A abuse-prevention restraining orders (a/k/a "ROs" in legal-speak), regarding un-emancipated children, under the age of 22.
I am not completely sure of the facts but I would suggest that you consult with an adoption attorney in your area. A few of the questions that I have is whether or not you were married at the time of conception or birth of the child. Under Florida law (it may be different where you live) if you are married to her during those times, you are the legal father and an adoption would not be necessary. Best of luck to you.
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If I understand your statement of facts correctly, you cannot adopt this child because you are already legally her father. If you signed the acknowledgment of parentage to get your name on the birth certificate more than a year ago, that is the same as a court judgment determining you to be the father.
Again, if my understanding is correct, you do not need to adopt your daughter to have your custody legally recognized. All you need to do is file a complaint for modification or, if the mother will agree, a joint petition for modification of the custody and support order in the court where your divorce action was held.
I have linked the Mass Trial Court Law Libraries' resource pages for adoption, paternity and modification for you to use as a primer to understand the issues that you should have lined up when you seek out an attorney to help you with your next steps.
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