When the New York Court of Appeals issued its landmark 2016 ruling to expand the definition of parenthood to nonmarried ex-partners of biological parents, it left open the question of how such a parent could have standing to seek custody without a preconception agreement.

But a Long Island trial court has become the first to offer an answer, ruling that a woman who was part of a now-defunct same-sex relationship may assert the same standing as nonbiological fathers in similar predicaments who seek custodial rights.

In a ruling issued Wednesday, Nassau County Family Court Judge Thomas Rademaker found that a woman identified in court papers as J.C. may seek custodial and visitation rights of two children who were born to N.P., J.C.’s former partner, with whom no preconception agreement was established by invoking equitable estoppel.

Under equitable estoppel, Rademaker wrote, courts usually find that nonbiological fathers can be deemed fathers in the best interest of the children if the children recognize the male to be their father or if the biological mother asserts as much.

The ruling is considered an outgrowth of the Court of Appeals’ ruling in In the Matter of Brooke S.B., 28 N.Y.3d 1, a case in which a preconception was found to exist, where the court said it would “be premature for us to consider adopting a test for situations in which a couple did not enter into a preconception agreement.”

The ruling in the Nassau County case was not the first post-Brooke ruling by a lower court, but the first to provide standing to a former partner in a same-sex relationship seeking custodial rights for children to which they have no biological relation.

In March, Suffolk County Supreme Court Justice H. Patrick Leis III granted “tri-custody” to a man and two women who raised a child together.

In April, Manhattan Supreme Court Justice Frank Nervo denied standing for a woman seeking joint custody of a child adopted by her former partner.