Kenneth Play had plans to celebrate his birthday with his girlfriend. But when she arrived at his Bushwick apartment, she wasn’t alone.

“She surprised me with two other lovers of mine for a birthday foursome,” said Play. The women were dressed in sexy cat-themed lingerie complete with light-up feline ears and face-paint.

The quartet went straight to Play’s bedroom.

“We used all kinds of sex toys and finished by having simultaneous orgasms,” the 36-year-old polyamorous “sex healer” and educator told The Post. “Then we had a bonus round in the shower.”

It was just another Tuesday night at “Hacienda Villa” — a seemingly pedestrian three-story Brooklyn brownstone that is actually a 14-bedroom sex haven for promiscuous sensualists.

Fourteen people, ages 21 to 45, reside there, enjoying a “sex-positive” lifestyle that encourages consensual romantic relationships with multiple partners. Thirty more are on the waiting list.

There’s one exception to the free-love lifestyle — housemates can’t have sex with each other.

The rule is “a way to eliminate drama and conflict,” said Andrew Sparksfire, 45, who founded the X-rated community in 2014.

Other rules include: no children or pets; housemates must be at least 21 years old; and each floor determines its quiet hours.

Residents frequently bring their partners, spouses — who live off-site — and even one-night stands to the residence for hook-ups. Sometimes roommates will swap partners for a night or more.

“It’s like the real version of the show ‘Friends’ — plus sex,” said one inhabitant who goes by Ryan and works as a chemistry data scientist. “I moved here from a nice big apartment in the Village because I love the community.”

Sparksfire, a real-estate investor and developer who bought the home in 2013, decided to turn the place into a communal residence after hosting polyamorous sex parties where guests would take part in orgies and sexual “play.”

“My house had become a center for sex culture,” said the UK native. “So I took that lifestyle from the sex parties and made a place where people lived it out 24/7.”

Roommates pay between $850 and $1,650 per month in rent (not including utilities), depending on bedroom size and whether or not it includes an en-suite bath.

Sparksfire splits his time between the house and a nearby apartment where his wife of one year, Beth, 32, lives. His 36-year-old relationship-coach girlfriend, Effy Blue, lives “harmoniously” in the apartment above Beth’s.

By day, the residents of Hacienda Villa are just a bunch of regular, hard-working New Yorkers — teachers, yoga instructors, financial executives and performers.

At night, they check their secrets at the door and let it all hang out.

“They could risk losing their jobs or being disowned by their families if they were open about their lifestyle,” said Lila Donnolo, 34, who joined the house in 2014 and hosts a sex-and-relationship podcast, “Horizontal with Lila.” “A lot of people just can’t understand or accept this lifestyle.”

A majority of the “members,” as they prefer to be called, consider themselves polyamorous and are in romantic and sexual relationships with more than one person.

Jealousy, they say, isn’t an issue.

“I love that my girlfriend has many partners,” said Play, who teaches an assortment of classes like “Kink Play Lab” and “Sex Science Social” in the house’s basement. “I don’t want my partner to feel neglected, so collectively we can provide the love she deserves.”

Play considers himself “mostly straight,” but dabbles with men.

“If a couple wants to give me [oral sex], or a woman wants me to make out with a man, then that’s sexy,” he said. “But if a woman’s not involved, I can’t get it up.”

Housemate Tiger, 30, is bisexual and gender fluid, not identifying as either strictly male or female.

“Being around this community gave me a supportive and safe space to explore my gender expression,” said Tiger, who non-sexually snuggles strangers for a living as a professional cuddler.

Three members consider themselves “monogamish,” but are open to other possibilities.

Sparksfire designed the house to echo the community’s sexual attitudes. The backyard has a hot tub for skinny dipping, as well as a bar and fire pit. There’s a sex library with reads such as “Stories From the Polycule” by Elisabeth Sheff, and the walls are peppered with photos of naked women. Coitus-themed novelties like a sex swing, leather whips and penis-shaped alcohol bottles are scattered throughout the apartment.

In one of the four common rooms, a giant teddy bear sits atop a round purple bed for “anyone to use,” said Sparksfire.

“I try to create an environment that when people walk through the door they feel comfortable in peeling off their clothes,” he added.

Outsiders are clamoring to get into the lavish 5,000-square-foot love shack. “We’ve gained a ton of interest especially in the last year,” said Sparksfire.

Each house applicant must go through a 60-day “tryout” period — including participating in weekly meetings where members discuss household issues and sex-party plans — and gain a majority vote from the members at the end.

Newbies are also highly encouraged to attend one of Hacienda Villa‘s over-the-top sex parties, especially if they’ve never been to one before. These events typically cost between $20 and $50 per person and often sell out in less than five minutes. Sparksfire said he receives thousands of requests to attend the invitation-only bashes. To break into the circle, partygoers must first attend as a plus-one before being added to the guest list.

The bacchanals usually have themes, such as doctors and nurses, or cabaret. During a church-themed party, guests dressed as sexy nuns and priests took turns flagellating each other. At one “Crime and Punishment” party a few months ago, the members set up a “slut court” on the second floor.

“People had to sign up stating how bad they’d been [then] a judge would decide their fate,” said Sparksfire. Some were sentenced to 10 lashes with a leather whip, others to harsh spankings.

The house also prides itself on being “an incubator for sex education” and roommates take turns teaching classes on sex in the basement. The classes are held several times a week and are open to the public for a prices ranging from $10 – $50. Among the curriculum are “Sex Hacking Play Lab,” “How to Throw a Sex Party” and “Gender Fluid Tango.”

“Squirting Play Lab” is especially popular, where professor Play teaches students about “cliteracy” and how to make women orgasm. It includes a discussion of anatomy and a live demonstration with another teacher.

The class is then encouraged to try what they’ve learned on each other.

“People walk away [with] a deeper understanding of female arousal,” said Play.

Prominent sex activists, such as “Ethical Slut” author Janet Hardy, also give talks at the house.

Despite the day-to-day prurience, Sparksfire insists this way of living is changing member’s lives for the better: “We’re helping people throw off the shackles of shame around sex.”