When Alaina Moore agreed to join her new boyfriend Patrick Riley on a sailing trip, she didn't really know what she was letting herself in for. This wasn't to be a couple of days of lazy yachting, but his lifetime dream: sailing his boat along the east coast of America for more than half a year.

"We ended up stormed in for three days, being pummelled by thunderstorms," she sighs. "Rain so thick we couldn't see land. We almost lost the boat.

Moore and Riley's seven-month adventure didn't break them up. Since the trip ended, they've married, formed a band called Tennis and recorded Cape Dory, an album of joyous, Phil Spectoresque seafaring pop. Personally and professionally, Moore could not be happier. "I can't imagine being in a band with anyone other than my husband.

Tennis are not alone in combining rock and relationships, and while couples have made music together for ever, nowadays it seems increasingly commonplace, less of a selling point and more of a fact.

Take Cults. Brian Oblivion and Madeline Follin knew each other from film school, but cemented their bond on a nine-hour drive to San Francisco, with music in the car. "It was a huge part of us getting to know each other," says Oblivion, Cults' guitarist. "'Oh, you love this? I love this, too.'" When pianist/bassist Follin started singing Oblivion's blissful, epiphany-like melodies, Cults was born. Sean Lennon and Charlotte Kemp Muhl were also already a couple – becoming harmony duo the Ghost of a Saber Tooth Tiger was, Lennon says, "us figuring out a way of spending all our time together".

"Any band is an alliance," says Wendy Fonarow, the Guardian's "indie professor" (and an actual associate professor of cultural anthropology). "But if you're forming a band to make music rather than meet new people to have sex with, then being in a relationship isn't really a problem. If music is part of the bond, it seems only natural to form a band."

Fonarow sees the upsurge in couples in bands as reflecting a wider generational shift in music, with women participating as equal partners, in contrast to an older culture that mostly cast women in bands as singers. "Part of the fantastic appeal of the White Stripes was the ambiguity of their relationship," she says, arguing that such bands changed attitudes. "Were they married or brother and sister? It was awesome and taboo at the same time."

However, the White Stripes broke up – first as a couple, then (last week) as a band. And while pop couples may have a stronger connection – initially, at least – than four mates who met at school, they face the combined tensions of being in a marriage and a band. And it can get messy.

"I know one band where the married guy couldn't take advantage of the easy sex that's on the road," Fonarow says. "The other guys could get away with cheating on their girlfriends, because they weren't there. It goes into issues of entitlement and double standards that we don't normally know are there."

The band survived, the marriage didn't. So do a couple becoming a band risk a musical Faustian pact?

From Sonny and Cher's I Got You Babe to Ike and Tina's emotion-wracked pop-soul, falling in – and out of – love is a recipe for fantastic pop. Songs seem to gain an extra frisson when the protagonists are involved. "We can say things to each other that you could never get away with, with anyone else," says Johnathan Rice of Jenny and Johnny (Jenny is Jenny Lewis of Rilo Kiley). "As a songwriter, that's amazing."

Cults don't make a big deal about their relationship. "We don't hide it," insists Oblivion, who met Follin in film school. "But we're not selling a cute couple image or pretending Madeline is single to sell tickets to horny teenagers." However, problems can begin when private relationships hit the spotlight. Fonarow sees something "ballsy" about a couple exhibiting their togetherness onstage, but cautions that because pop revolves around selling attainability in an arena of sexual longing, pop couples risk "a potential for envy among a part of the audience".

And criticism can be doubly hurtful if neither partner can step away. Moore is still wincing at one review of Tennis that described them as "nauseatingly cute". Lennon is frustrated with comparisons between his project and the musical relationship between his parents, John Lennon and Yoko Ono. "People have criticised us for trying to be like them which is ridiculous. There was one picture of Charlotte in a hat. She'd never even seen a picture of my mother in a hat!"

"Being able to support each other in that kind of environment is really important," suggests Paula Hall, a therapist for Relate, the relationship counselling service. "I've had clients like that and celeb status involves a whole other level of pressure, especially if they're reading about each other in the media."

Within the music industry, female musical partners are still sometimes regarded with suspicion. "Everyone has this idea of Serge Gainsbourg and Jane Birkin: the woman being pretty and prancing around while the guy writes all the songs," says Kemp Muhl, whose musical input in Saber Tooth Tiger is the same as Lennon's. Moore has arrived at venues where Tennis are playing to be told: "'Sorry Miss, no girlfriends on the stage.' I've lost count of the number of times that's happened."

Such incidents can strengthen a couples' ties, but even the most solid relationships will be tested in the environment of a rock tour, crammed inside a bus, surrounded by petty jealousies, bitchy rival musicians and predatory fans. Jenny and Johnny argue that touring together is preferable to the loneliness experienced by single musicians. Rice insists he doesn't notice when women hit on him. "Yeah, right!" Lewis fires back. Even so, she admits: "With Johnathan there's always someone to walk me to the bus. Before that it was just me and the wolves – the 1%, obsessive fans that look like Jeffrey Dahmer."

For Hall, the time pop couples spend together and the in-your-face nature of sexual display in the music industry is preferable to the more secretive goings on a couple may face in another work environment. "They're not going to wonder what he's up to with his secretary or what the new bloke in accounts is like," she points out. Occasionally, though, dalliances do begin close to home. In her Britpop memoir Different for Girls, Sleeper's Louise Wener describes the mayhem that erupted when she switched boyfriends from guitarist Jon Stewart to drummer Andy Maclure, thereby "risking the future of the band and the sanity of everyone around [it] for a sordid intra-band fling".

Commitment issues – where one party is more dedicated to the band – can also wreck relationships, as can the mundaneness of spending so much time together, doing the same thing. "I get a lot of couples who work together but it's not quality time," explains Hall. "They're not going out for meals in the evening and catching up like they would." And for her, the biggest threat to any relationship is communication breakdown.

Perhaps the lifespan of a band has parallels with a marriage anyway: they meet, make music, get signed, tour. It's exciting. Then at some point comes a bump, where they have to write a second album or realise they're stuck in a studio with people they no longer have much in common with. And just as relationships turn toxic, so can bands – especially when a relationship within it ends. For example, when Elizabeth Fraser stayed in the Cocteau Twins with Robin Guthrie after their relationship had failed, the resulting acrimony caused what she called "lasting damage". When Richard and Linda Thompson's marriage ended, Richard was horrified that Linda insisted on going ahead with a US tour – the pair had no contact except on stage.

However, some former couples do play together after their romance is over, such as Blondie's Deborah Harry and Chris Stein. Jenny Lewis – whose own parents were travelling entertainers who broke up – still also performs with ex-boyfriend Blake Sennett in Rilo Kiley. "The music was more important than the torture of being around him," she says, drily.

"It depends on the reason for the separation," says Hall of the likelihood of a former couple continuing to work together. "If it was a friendly drifting apart it makes no difference if you work together. But if one of you has gone off with someone 10 years younger it's untenable, really." She adds that a downturn in success can also spell trouble: "When people work in different professions, one can support the other emotionally and financially if things go wrong. If a band fails, you're going down together."

However, Hall's expert prognosis for couples involved in bands is good. "Intimacy has many areas – aesthetic, creative, career, social, intellectual – and many couples don't have the opportunity to share all those like a couple in a band," she explains. "Unfortunately they will share the same problems, and hit crises together, like working hours, or the question of whether to become parents. On the other hand, if it's a passion you share equally, music could form an absolutely fantastic bedrock for your relationship. It's really nice to have someone who understands what you do."