A gay woman who claims she was both the daughter and "wife" of multimillionaire IBM heiress Olive Watson is suing for a stake in the Watson family fortune.

Patricia Spado was Watson's domestic partner for more than 10 years until 1992, when the couple split up, according to court records. Before the breakup, Watson -- the daughter of IBM founder Thomas Watson Jr. -- legally adopted Spado in Maine in order to circumvent state laws that forbid them to marry.

At the time, Spado was 44 years old and Olive Watson was 43. Spado contends that the unusual arrangements were intentionally designed to allow her to become Watson's legal heir. Since Spado was legally adopted by Watson, she is technically Thomas Watson Jr.'s granddaughter.

Now, however, the elder Watson's other grandchildren are contesting Spado's claim to a share in a family trust reportedly worth millions of dollars. Thomas Watson earmarked the trust specifically for his grandchildren, and it became active when he died in 1993. He did not know about his daughter's arrangement with Spado, according to court records.

Thomas Watson's blood heirs are arguing in probate courts in Maine and Connecticut that he intended the trust solely for children born to his children, and not their adult partners.