Some states require a couple to be married for at least a year before one of them can adopt his or her spouse's children. Adopting a stepchild is a way to unite the family in a legal and symbolic manner. For younger children, it can also provide a sense of long-term commitment by their stepparent to more than just their mother or father's needs but their own as well. After adopting a stepchild, that child will be under your custody. If anything happens to the marriage, the child will be treated like a biological child. This means you would be responsible for child support or other arrangements.
Unfortunately, adopting your spouse's child is not always a simple process. It may be necessary to ask the noncustodial parent to terminate his or her parental rights before you can adopt the child. Child support payments will cease and the child will be issued a new birth certificate, as in a stranger adoption. Because many stepchildren have experienced a divorce, it's important and required by law that any child over the age of 10 consents to the adoption by a stepparent. Children may love you and accept your role in their custodial parent's life, but being adopted can make some feel guilty and as if they're betraying their other parent.
Based on the results of various studies, children are more content in a home where they live with a stepfather rather than a stepmother. The adoption of stepchildren by a male spouse is more common as well.