The way it is looked at legally, is while you were married, you contributed to the childs well being. Part of your income did go to support the food on the table, the roof over thier heads...etc.
Sorry but i might have to disagree with you. While you were married there was no consideration about a new parent or step father contributing to the child's well being. that is for the biological father only. Otherwise can you imagine non custodial would be looking for relief in cs payments for situations where the mother re-marries?
They suggest that a parent who includes a child or has the child or children as part of the family then becomes finacially required to pay support to a step child. They actually in the wording make no reference to the finacial contributions..because they have already legally made any contributions immaterial.
However...Jax in fact there is legal precedent that suggests a mother cannot legally pursue a cs order on a step parent if she has not received one from the biological father. A number of lawyers do not like playing this card but there is some case law supporting this premise.