This article has been corrected. You may view this article’s correction here.

On Friday evening, the brothers of Psi U gathered in a suite in Pierson College to play a game of Kings.

They sat around with cold cans of beer; the deck of cards were shuffled and laid out on the table. As soon as a five was drawn, the brothers took swigs and popped open new beers. When a six was flipped in a later round, it was time for the “chicks” to take up their drinks.

Any other fraternity might have invented another rule to make up for the absence of girls. The guys might have skipped the round altogether. But for this group, a six did not interrupt the game. The brothers of Psi U bumped cans, yelled cheers and watched their three female members take their turn.

Psi U, after all, is not like any other fraternity at Yale. This fall, the original group of roughly 20 brothers accepted five women to become “brothers,” along with four new male brothers. Their brotherhood, members said, found no reason to limit their membership to men.

“Most frats hang out with chicks because they want to hook up with them,” Psi U brother Avinash Gandhi ‘10 said. “We just like kicking it with them.”

Although once part of the Psi Upsilon International Fraternity, the Yale group has been independent since 2007, when its members decided they did not want to pay annual fees to the fraternity’s national chapter. The organization further departs from traditional notions of Greek life by not having a house of its own or a classic rush process.

Psi U’s laid-back philosophy, Gandhi explained, justifies their decision to extend membership for girls. Many brothers agreed that the overarching ideals, “More is better” and “All friends are welcome,” are just a few of the fraternity’s main tenets. Simply put, four male members of Psi U said there was “no reason not to let in girls.”

But at the bottom of it, fraternity brother Justin Berk ’10 admitted that the first accepted female was a girlfriend of one of the brothers. Berk explained that the girlfriend brought along her friends to Psi U parties and soon they became a bonded, co-ed group.

Still, he said, the chemistry between members is hardly romantic. After all, he joked, only 20 percent of their female membership — or one out of five girls — is involved in a relationship with one of the guys.

Callie Gleason ’11 joined Psi U this fall with three of her suitemates. Despite the stereotypical, often gruesome rituals of hazing associated with fraternities, Gleason said the girls participated in only one rush event — a “pub crawl” in which Psi U brothers mixed drinks and set up different drinking games in each of their rooms.

Gleason, who is also a member of the all-female a cappella group Proof of the Pudding, said she did not need the all-female community or extra time commitment of a sorority. Gleason emphasized that she was just one of the guys, playing beer pong and watching movies, during the weekend. Another female member, Justine Leichtling ’10, said she enjoyed the reputation that came along with joining the fraternity. “I still kind of think it’s funny there are women in it,“ she said with a laugh. “That’s partly why I’m so proud of it.”

Gandhi said that “the women are called brothers because everyone in the frat is equal.” Calling the new female members “sisters,” he noted, would create an unnecessary distinction between members.

And while this model of inclusiveness is lauded by some female activists, other single-sex groups rejected the possibility of admitting the opposite sex.

Yale Women’s Center Board Member Emily Hoffman ’10 said she hopes Psi U’s decision to allow women to join represents a step forward for gender relations in Yale’s social scene.

“Since so many of the problems with fraternities have to do with gendered power differentials, co-ed membership might serve to disrupt these dynamics,” she said. “It would be very worrisome if co-ed membership did nothing to alter the atmosphere.”

But members of many of Yale’s official sororities and fraternities said they found the admission of the opposite sex problematic.

The vice president of development for the sorority Kappa Alpha Theta, Julianne Carlson ’10, said the mixing of genders violates the purpose of a sorority or fraternity.

“The value of a frat is to maintain brotherhood,” she said. “You can’t call it a fraternity if girls are involved.”

Jason Gilliland ’10, the vice president of recruitment for Sigma Phi Epsilon, agreed that a fraternity tries to cultivate a certain culture based on “all guys.” (SigEp is a member of the North-American Interfraternity Conference, which clearly states that “Fraternity-chapter women’s auxiliary groups — i.e. ‘little sisters’ — are not allowed.”)

The fraternity Sigma Chi is also a member of this Conference. Sigma Chi’s social chair, Kevin Symcox ’10, said he is fairly positive that his fraternity would never consider admitting female pledges. “The Dartmouth chapter did a similar thing a few years ago and had to break off from the national chapter,” he said.

But the formalities of typical fraternities, let alone official organizations, do not apply to Psi U, many members said. Even in its early conception, Psi U co-founder John Mullins ’07 said the fraternity functioned to bring together friends. The fraternity was founded in the winter of 2004 by a diverse group of sophomore friends, including members of the football team as well as literary magazines, he said.

“Most frats are steeped in history, with specific things they do every year and one kind of kid they always attract,” Mullins said. “Psi U is much more flexible; there are no rules that can’t be changed.”