In their 14-year relationship, Patricia Spado and Olive Watson spent only five nights apart. They lived in New York, spent summers in Maine, and shared the more practical pieces of a life together — a home, a joint bank account.

But in a time long before civil unions or gay marriage, Watson wanted to ensure that her partner would be taken care of when she was no longer there. So, at a small courthouse in coastal Maine, she adopted Spado.

Fifteen years later, the adoption is being challenged in courts in Connecticut and Maine as Olive Watson's family parcels out the family fortune — and contests their newfound heir.

The case, according to gay activists, is rare and offers an example of how far same-sex couples have gone to attain financial and inheritance protections that married couples take for granted.

"It shows what people are driven to when they don't have access to marriage and the conventional way of forming a family," said Mary Bonauto, an attorney with Gay & Lesbian Advocates & Defenders, the Boston-based group that won the legal battle that introduced gay marriage to Massachusetts.

At stake is a share in multimillion-dollar trust funds that Olive Watson's father, Thomas Watson, who built International Business Machines into today's IBM computer colossus, set up for his grandchildren. He died in 1993, unaware of the adoption. His wife, who died in 2004, apparently learned of it from her daughter.

With the deaths of both parents, the trusts' beneficiaries — grandchildren, at least 18 of them — became eligible for cash payouts at age 35. But when Spado's lawyer notified the trusts that she was a potential beneficiary as a legal granddaughter, the family challenged the claim in probate court in Greenwich, Conn., where Thomas Watson lived at the time of his death.

Spado and Olive Watson aren't together anymore. They separated in 1992, and while Spado received about $500,000 from Watson, there is nothing in court records to show any arrangement beyond that.

A judge ruled that Thomas Watson did not recognize Spado as his granddaughter and did not intend for her to benefit from the trusts. "It is reasonable to conclude that Watson intended to benefit only those grandchildren who had a typical parent/child relationship with his children," Judge David Hopper wrote.

The size of the estate has not been estimated in court documents, and principals in the case did not respond to requests for comment. Lawyers for Spado and Watson also did not respond to questions about the case.

Spado has appealed. In the meantime, the family trusts are trying to have her adoption annulled in Maine, where they would have to prove deception or fraud.

Briefs filed with the Maine Supreme Judicial Court, which heard an appeal on a technicality, indicate that the judge who approved the adoption never knew that Olive Watson and Spado had a sexual relationship.

New York, where the couple had been living at the time, barred the adoption of a homosexual partner, but Maine had no such restriction. Nor did it have a provision like Connecticut's that prohibits a person from adopting someone older — Spado, 44 at the time, was a year older than her adoptive mother.

However, the Maine adoption law required that the adoptee had to be living in the state, and the two sides are at odds on whether spending part of each summer vacation on Maine's North Haven island met that requirement.

The couple met in 1978 while Spado was working in Los Angeles. Watson rented a residence in California in order to be with her lover, who later abandoned her career and moved with Watson to New York.

They held joint bank accounts, owned real estate together and exchanged durable powers of attorney and health care proxies. Watson amended her will to name Spado as sole beneficiary.

After their breakup, Watson paid Spado the $500,000 settlement in exchange for relinquishing her claim to certain real estate. But the settlement was apparently not intended to terminate Spade's right to her inheritance as a granddaughter.

According to a court brief filed by Spado in Maine, a letter signed by Watson shortly after the breakup confirms "our agreement that I have not and that I shall at no time initiate any action to revoke or annul my adoption of you."