An adult may adopt another adult. This is usually done for sentimental reasons. It will affect inheritance rights should the original parents, the adoptive parents, or the adoptee die without a will.
Performing such an adoption requires that a Petition for Adoption and Decree of Adoption be filed in Circuit Court. The adoptee must consent in writing to the adoption. It is not necessary to obtain a consent or serve notice upon the original parents. This adoption process takes about 2 months.
A change of name may be done as part of the adoption process. After the Decree of Adoption is signed, the adoptee will receive a new Birth Certificate from the state where he/she was born. It will show the adoptive parents as being the legal parents, along with the change of name if desired.