This scenario is becoming a more and more popular one with the trend in same sex marriages as well as blended family scenarios where a stepparent adopts the biological child of their spouse. Once a party adopts a minor child, that party is the minor child’s legal parent. That parent is entitled to the same rights as a biological parent under law. Thus, the answer, generally, is yes, if a spouse adopts the other spouse’s biological child and the parties subsequently divorce, the adopting spouse has standing and the ability to request custody, just as a biological parent could.
If the spouse is only a stepparent, however, they are not really afforded the same rights as biological parents. There are very specific instances when a stepparent can request custody of a minor child, but generally the minor child would have to be physically in their care when they do so, or, if the minor child is not in their care at the time they file, there is other criteria that a stepparent must meet before they can file a custody petition. Any party can file for custody of a child that is not biologically theirs if the minor child has been in their care for a certain period of time (and not in the care of a biological parent) and if other criteria is met.
While no one wants to enter into a relationship thinking about divorce, it is important to think about the consequences of a marriage ending and the impact it can have on custody and visitation decisions upon a divorce, if you are contemplating allowing your spouse to adopt your biological child.