I would like to find out how I need to go about adopting a 21 year old. Does anyone have the know how?:confused:

An adult adoption is when someone adopts a person who is 18 or over and not related to them. An adult adoption changes the legal rights of the adoptive parent and the adoptee. Adoption of adults differs from the adoption of children in three major ways:

No parental consent is required and notice is not required to be served on the natural parent.
No agency investigation is required (although the court may order one if it is deemed necessary).
Adult adoptions can be terminated by the adoptee on petition to the court and notice to the other party.
FORMS REQUIRED

There are no fill-in-the-blanks forms for adult adoptions. There are three or four main documents-also known as pleadings--that must be filed with the court. These documents must contain very specific language. You can consult law library resources to find models of these documents, which you will use as guidelines for typing up forms/pleadings customized to the facts of your own situation.

The Adoption Agreement. This states that the parties agree to assume toward each other the legal relation of parent and child, and to have all of the rights and be subject to all of the duties and responsibilities of that relationship.
The Petition (for Approval of Adoption Agreement). This document must provide many specific details, including the ages of the parties and the nature and length of their relationship, the reason(s) the adoption is being sought and why it would be in the best interest of parties, and the request that the court approve the agreement of adoption.
The Order of Adoption (also called the Decree). This is presented to the judge at the adoption hearing, for him/her to sign. This becomes the Decree.
Consent(s). In addition to the above three documents, if the adopting parent or the proposed adoptee is married, a spousal consent document also will be required.
PROCEDURES

Type the Agreement (it does not have to be notarized), the Petition, the Order, (and Consent forms as needed). Make copies for all parties and for the Court.
File the Petition with the Clerk of the Probate Court, and ask to set a hearing.
Pay the filing fees.
Go the hearing; take with you the Agreement and the Order for the Judge to sign.

Many states have some specific rules, it can not be done for purpose of a same sex relastionship to give the other partner rights not available because they can not marry and some other restrictions.

But you hire an attorney and file adoption paper work,