Adoption by Stepparents or Domestic Partners
Stepparent adoption is the most common type of adoption and is generally a simpler process than adopting a nonrelative. You will need the consent of the child's other birth parent to adopt a stepchild, unless that parent's rights to the child have been terminated. In a few states, same-sex domestic partners can follow the same procedures as for stepparent adoption.
Deciding to adopt
The decision to adopt the child of your spouse or domestic partner may be complicated by the emotional issues it presents for the child. If the other biological parent is still living and visits the child, it may be stressful to the child to hear they are not officially related to their birth parent anymore.
Though there may be no legal barriers to adopting a stepchild, it may not be advisable because of the impact on the child. Consider carefully whether the adoption is best for the child before proceeding.
If the other birth parent does not want to give consent and still has parental rights to the child, there are options open to stepparents looking to adopt. You would need to ask a court to terminate the other parent's rights to the child, either by proving the biological parent abandoned the child or that the person is not actually the child's biological parent.
The adoption process
In most states, the adoption process is fairly simple for stepparent adoptions, aside from the issue of getting consent. Parts of the ordinary adoption process may be shortened or waived altogether, such as the home study and the traditional waiting period. In some states you may need to be married or with your partner for longer than 1 year.
You will need to demonstrate that you are willing and able to take on financial and legal responsibility for the child. Note that adopting a stepchild will end the other biological parent's responsibilities to that child, including child support payments.
You will also want to get an experienced adoption attorney to make sure your adoption is complete and legal. When the adoption is final, you can apply for a new birth certificate.
U.S. Dept. of Health and Human Services: Stepparent Adoption Factsheet for Families (http://www.childwelfare.gov/pubs/f_step.cfm)
Adoption Connection: FAQs for Stepparents (http://www.adoptionconnection.org/stepparents.asp)
Related Legal Guides:
Adoptions by Relatives (https://www.avvo.com/legal-guides/adoptions-relatives)
Adopting from Foster Care (https://www.avvo.com/legal-guides/adopting-from-foster-care)