There is a way for a stepfamily to be considered equal to a first family in the eyes of the legal system. If you adopt your stepchildren, then all the rights of the noncustodial parent are severed, and you and your stepchildren gain all of the rights afforded to parents and their kids.
However, though adoption by stepparents is on the rise, it’s still a difficult thing to do if the other biological parent is still living. First, you and your husband have to get buy-in from the kids. The older they are, the more say they have in the eyes of the law.
Second, the biological mother has to sign away all her rights to the child or you have to prove beyond a doubt that she is an unfit mother. Because it’s very hard to prove a mother is unfit to parent her children and it’s a permanent decision, stepmothers usually don’t attempt adoption unless it’s an extreme case—if Mom is an incarcerated drug addict or severely abusive, for instance. When Mom is deceased, you can legally adopt stepchildren as long as Dad and the children find it acceptable.