One consequence of denying gay couples the right to marry is that it forces people to resort to legal convolutions to protect their family’s financial interests. This problem is currently at the center of an intriguing lawsuit involving Olive Watson, a granddaughter of Thomas Watson Sr., the founder of I.B.M., and Patricia Ann Spado, her former lesbian partner of 14 years. Sixteen years ago, when she was 43, Ms. Watson adopted Ms. Spado, then 44, under a Maine law that allows one adult to adopt another. The purpose was to allow Ms. Spado to qualify as an heir to Ms. Watson’s estate. It was a legal path used over the years by an untold number of same-sex couples who had been denied a straightforward way to establish inheritance rights through marriage.