Custody and visitation are no longer based solely on biology or adoption.

In a landmark ruling, the New York Court of Appeals has revised the legal definition of “parent” under New York’s Domestic Relations Law.

The new criteria no longer rely on a 25-year-old precedent that defined “parent” exclusively as a person related by biology or adoption to a child. The Court found that this rule had “become unworkable when applied to increasingly varied familial relationships.”

The August 30th decision in Brooke S.B. v. Elizabeth A. C.C. followed an appeal on behalf of a child seeking time with both mothers after his same-sex parents split up.

Brooke and Elizabeth began their relationship in 2006 and announced their engagement the following year.

In 2008, Elizabeth became pregnant with their child through artificial insemination. Though Brooke had no legal or biological ties to the child, a boy, she maintained a close relationship with him for years, giving him her last name and raising him jointly with Elizabeth, before separating in 2010.

Three years later, Elizabeth tried to cut off Brooke’s contact with the boy.

“This is a major step forward for same-sex couples and especially for the children of those parents,” says Eric Wrubel, who argued the appeal. “Tying the definition of parenthood to biology or adoption was no longer viable. This new ruling will help protect children, regardless of their parents’ marital or financial status.”

Under the new law, non-biological, non-adoptive parents will no longer be automatically barred from seeking custody and visitation. The Court stated that a party can establish standing in such cases by showing “by clear and convincing evidence that the parties agreed to conceive a child and to raise the child together.” The Court left open the question of whether a party who formed a parent-like relationship with a child after conception can establish standing.