COLUMBUS, Ohio—Long before the federal government and individual states enacted legislation defining marriage as a union between one man and one woman, Jack Towarnicky, associate vp of benefits planning at Nationwide Mutual Insurance Co., had the foresight to design a domestic partners health insurance program for Nationwide employees.

But the intent of the program, which was launched in 2000, wasn't to attract same-sex partners, he said. Rather, it was to enable other household members of Nationwide employees, such as their adult nonstudent children, their parents, even uncles and aunts, to have access to affordable health insurance, Mr. Towarnicky said.

Still, the Columbus, Ohio-based employer received considerable flak from the community, with local television stations airing reports lambasting the company's liberal stance on same-sex marriage.

Eventually the controversy died down, but Nationwide continued to quietly administer its Household Members insurance program.

To qualify for coverage, household members must be dependent or financially interdependent with the employee. Target groups are adult nonstudent children and same- or opposite-gender partners.

As it turns out, the vast majority of household members enrolled in the plan are, in fact, the adult nonstudent children of employees. But there are also a few "aunts in the plan," said Mr. Towarnicky. In addition, the plan covers several nieces and nephews, sisters and brothers, fiances and grandparents, among others. Altogether, about 500 individuals are enrolled.

Nationwide makes the same contribution to the premiums as it makes for single coverage, with the employee picking up the tab for the remainder. If the individual seeking coverage does not qualify as being a "dependent" under the federal tax code, then the employee contribution is made on an aftertax basis. If they do qualify, the contributions are pretax. The contributions are not taxable income to the employee as long as the individual being covered meets the definition of dependent under Section 152 of the IRS Code.

The program so far has been a success, both in terms of meeting the needs of employees as well as claims experience. Average loss ratios ranged between 26.5% in 2000 and 77.9% in 2006. But because the loss ratio surged to 132.7% in 2007, next year will be the first time since its inception that premiums will be raised for participants, Mr. Towarnicky said.

In part because of its Household Members program, for the last five years Nationwide has received a score of 100% in the Washington-based Human Rights Foundation's Corporate Equality Index, which ranks employers' treatment of gay, lesbian and transgender employees.