Sometimes families go through very difficult situations such as a divorce. When this happens in blended families, the stepparent could still be very involved in the stepchild's life and desire to adopt that stepchild, and that child could desire to be adopted by that stepparent as well.
This happens more often than one might think.
Unfortunately, stepparent adoptions cannot be completed after a divorce. A stepparent adoption is unique because it allows one biological parent to retain their parental rights while another parent is allowed to step in as the second parent and adopt their child. This is possible because the law allows a biological parent to agree to the stepparent adoption of their child by their spouse.
Once the divorce occurs, a stepparent adoption is no longer possible. What is possible is an adoption. For an adoption to happen, both biological parents have to relinquish their parental rights to the child and agree to another adult adopting that child. There is no other way to complete the adoption after a divorce.
My recommendation is always to complete a stepparent adoption as soon as possible so if a divorce ever occurs in the future, the stepparent will retain legal rights to the child.