Ala. Code § 26-10F-6: Who May Be Adopted.

An adult may be adopted under any of the following conditions:

(1) He or she is an individual with a total and permanent disability.

(2) He or she has been determined to be an incapacitated person as defined in Section 26-2A-20.

(3) He or she consents in writing to be adopted and is:

a. Related in any degree of kinship to the petitioner or petitioners, as defined by the intestacy laws of Alabama;

b. A stepchild or former stepchild by marriage; or

c. A United States citizen and the court is satisfied that there exists a multi-year relationship akin to that between a parent and child and the adoption is for a legitimate purpose.

(4) He or she had been in a de facto parent-child relationship with each petitioner for at least one year during the minority of the adoptee, and each petitioner has maintained a continuous familial relationship with the adoptee. This subdivision shall include, but is not limited to, a foster parent relationship with the adoptee.