Once you are married to one of the child's parents,you then are the child's step-parent,as long as there is marriage by law you then become the legal step-parent,if there is no marriage you are then referred to as my moms boyfriend or my dads girlfriend.
What Is The Legal Definition Of Step-parent? My Mom Got Divorced & Remarried After I Was Grown (moved Out & Married Myself). Is The Man She Married Legally Considered My Step-father (since There Was No Parenting Involved) Or Just My Mom's Husband?
A step-parent comes into play when you become divorced from your partner and you already have a child. A step-parent is a guardian that replaces a mother or father,but to be a legal step-parent you have to marry one of the parents.