The Beloit YMCA told Genia Stevens that she and her female partner to join as a family. According to Stevens, the front desk clerk told her, "No, we only allow a husband, wife and children to use the family membership because that’s what a family is."
The answer is not quite true, since the Beloit Y allows single parents and their children to join as a family. In fact, Stevens has joined the Y with just such a membership, even though she's not truly single - although the government and, apparently, the Beloit Y, define her as such by default.
The Beloit YMCA is now looking at its policy to consider broadening its definition of "family" to include unmarried partners (same-sex or opposite sex) and extended families that live in the same household. But it's made no promises to change the policy.
You can read more in the article from The Wisconsin State Journal.