In a landmark decision that narrowly but clearly alters how New York defines parenthood, the state's highest court on Tuesday found that when an unmarried couple who decided to conceive children together splits up, a non-adoptive, non-biological parent has the right to seek visitation or custody.

The Court of Appeals ruling, authored by Associate Judge Abdus-Salaam, reverses a 25-year-old precedent that had barred non-adoptive, non-biological parents from claiming parenting rights.

The decision in the consolidated cases Brooke B. v Elizabeth A. and Estrellita A. v. Jennifer D., focused on changing social and legal definitions of family and parenting, which the court said necessitated an updated interpretation of the laws governing visitation and custody.

"In light of more recently delineated legal principles, the definition of 'parent' established by this Court 25 years ago .... has become unworkable when applied to increasingly varied familial relationships," the court wrote.

Both lawsuits were brought by women who with their former partners had decided to conceive a child through artificial insemination. In each case, the partners carried the child, who was raised by the couple. Each couple ultimately broke up, leading to the underlying conflict regarding parenting rights.

From that point on, the cases diverged. In the first case, Brooke B. filed a suit against her former partner, Elizabeth C.C., claiming she was entitled to joint custody and visitation of their child, a position endorsed by the child's Family Court-appointed attorney. Elizabeth argued that Brooke was not the legal parent of the child and sought dismissal of the suit. Citing precedent set in the 1991 case Alison D. v. Virginia M., the Family Court judge presiding over the case threw out the suit.

A fairly straightforward dispute. The details of the second case, however, are not so simple.

After Estrellita A. and Jennifer D. broke up, Jennifer filed a suit against her former partner seeking child support, which Estrellita said she wasn't responsible for providing. While the support case was pending, Estrellita filed her own suit, seeking visitation rights. Jennifer's child support petition was approved by Family Court on the grounds that the nature of Estrellita's relationship to the child made her its parent.

Estrellita then updated her visitation suit to include the Family Court ruling as evidence she was entitled to visitation. Jennifer asked the court to reject Estrellita's visitation claim. Recognizing the inherent inconsistency in Jennifer's position—i.e., arguing that Estrellita wasn't the kid's parent in the visitation case after claiming that she was in the child support case—the Family Court said Estrellita deserved visitation rights. Jennifer appealed to the Appellate Division, which upheld the Family Court ruling, which she then appealed to the Court of Appeals.

The Court of Appeals limited the scope of its opinion to instances in which two parents together decided to conceive and raise a child. The court declined to rule on whether non-biological, non-adoptive parents have parenting rights in situations where the couple didn't decide to conceive a child, but after conception decided to raise it together.

The court noted that Family Court retains power to make custody and visitation decisions in individual cases based on its discretion.