Many people eventually move on and have second marriages, and even more children, after a divorce. In these situations, particularly if the noncustodial parent is not actively involved in the children's lives, a stepparent may consider adopting his spouse's children. While this is possible in some circumstances, it's important to understand what needs to happen for the courts to allow this.
For a stepparent adoption to occur, the birth parent generally has to give consent, and this is not quite as easy as it sounds. The courts do not usually allow parents to give up their children just because they want to, but if a stepparent is in the picture and willing to take over the financial, physical and emotional support of the child along with the child's custodial birth parent, it may be a possibility.
In some cases, however, the birth parent's consent is not needed. The basic rule is if the birth parent no longer has parental rights, he or she doesn't have to consent to the stepparent adoption. Parental rights differs from custody, however. Just because one parent has sole legal custody does not mean that the other parent no longer has parental rights. This is true even if the noncustodial parent does not exercise his visitation rights.
In some situations, it is possible to terminate a birth parent's parental rights or have the person declared unfit, but it can be a challenge. A family law attorney can go over the details of your case and let you know if you need consent for a stepparent adoption or if you will need to pursue having the birth parent's rights terminated.
Source: FindLaw, "Stepparent Adoption FAQ's," accessed July 24, 2015