M. H. B. (Marilyn) (plaintiff) and H. T. B. (Henry) (defendant) were married for approximately 10 years but separated. During the marriage, Marilyn had given birth to a daughter, K. B. Several months later, Henry learned that he was not K. B.’s father but continued to treat K. B. as if she were his biological daughter by providing her with emotional and financial support. Additionally, K. B. shared the same last name as Henry and was registered on all documentation as Henry’s child. Subsequently, Marilyn and Henry executed a separation agreement providing that Marilyn would retain custody of their children, with visitation reserved for Henry, and that Henry would pay $600 in child support. The following year, Marilyn and Henry obtained a divorce in Wisconsin, stipulating that their children were born of the marriage. Several years later, Henry filed a petition in Wisconsin, seeking to obtain custody of his son and K. B. The court transferred the matter to a New Jersey court, where Marilyn filed a petition seeking to retain custody of their children and increase child support. Henry counterclaimed, seeking the same relief as in Wisconsin. In the alternative, Henry argued that he should no longer be required to pay child support for K. B., because he was not her biological father. After a hearing, the trial court held that Henry was K. B.’s father for all purposes and concluded that the doctrine of equitable estoppel precluded Henry from denying the duty to pay child support on behalf of K. B. Henry appealed. The appellate division affirmed. The New Jersey Supreme Court granted certiorari to review.