A court in New York has thrown out a definition of parenthood that specified a “biological” connection to a child.

Today, the New York state Court of Appeals issued a landmark ruling overturning the 1991 Alison D. v. Virginia M decision that defined a parent as someone with “biological or adoptive” connections to a child.

It follows a case concerning a former same-sex couple, when a biological mother had retained custody of children but her ex-partner waged a legal challenge for access rights.

According to the NY Daily News,  the state Court of Appeals ruled that the specified “standard had become unworkable in light of society’s increasingly varied familial relationships”.

Judge Sheila Abdus-Salaam wrote: “We agree that, in light of more recently delineated legal principles, the definition of ‘parent’ established by this Court 25 years ago in Alison D. has become unworkable when applied to increasingly varied familial relationships.

“Accordingly, today, we overrule Alison D. and hold that where a partner shows by clear and convincing evidence that the parties agreed to conceive a child and to raise the child together, the non-biological, non-adoptive partner has standing to seek visitation and custody.”

The decision only impacts cases where the non-biological parent was part of the decision to conceive and raise a child.

Decisions in individual suits will still be decided on a case-by-case basis and based on “what is determined to be in the best interest of the child”.