Some tennis doubles partnerships make perfect sense. Identical twins Mike and Bob Bryan have spent a lifetime sharing toothbrushes, completing each other's sentences and polishing a sixth sense on the court.
But the men's and women's tours are littered with strange bedfellows. Take Rohan Bopanna and Aisam-Ul-Haq Qureshi. Bopanna, from India, and Qureshi, from Pakistan, hail from uncomfortable nuclear neighbors that have fought three major wars since 1947.
The tandem has climbed into the top 35 this year while becoming unofficial doubles diplomats, promoting peace through their play and proving that incongruous names on paper can work magic in practice.
"Until the last year, I never thought we could make a change in people's lives through sport," says Qureshi, 30, who made news headlines in 2002 when he teamed up at Wimbledon with Amir Hadad of Israel. "It made us realize we can do something bigger than sport: Send a message of peace."
The modern doubles partnership is born of many circumstances, often ends in divorce and requires years of work to succeed. In other words, it's a lot like marriage.
And it's not uncommon for players to use relationship language to describe what makes a team succeed or fail.
"There might be the initial spark," says American Bob Bryan, explaining why so few teams stick together beyond a year or two. "But once that honeymoon period wears off, it takes effort to jell."
"Finding a partner is like trying to find a girlfriend," adds the aptly named Wesley Moodie, who has a reputation for unexplained partner swapping. "You exchange numbers and go from there. Hopefully the breakups aren't too bad."
Doubles serves different purposes to different players. Some singles players avoid it altogether or dabble in doubles, while others make their living as doubles-only specialists.
Motivations vary. Some play for prestige and titles. Some play for extra change in their pocket. Others compete for fun, or to hone their singles skills. Some, such as Jelena Jankovic, do it to avoid practice.
"They all know I don't play doubles," says the fifth-ranked Serb, who nevertheless played with fellow IMG/Bollettieri product Shenay Perry of the USA earlier this year on a last-minute whim when Perry's partner backed out. "I'm just looking to work on my game."
Occasionally, players suit up on a lark, as when 6-10 Ivo Karlovic of Croatia and 6-91/2 John Isner of the USA joined forces at the 2008 Australian Open to earn Guinness Book accolades as the tallest team on record.
Or consider the 1980s retro team of Kimiko Date Krumm of Japan and Yayuk Basuki of Indonesia. Date Krumm and Basuki took to the court together at this year's Australian Open to form perhaps the oldest combined team in history. Their collective age: 78 (each is 39).
"We've known each other for a long time," Basuki says in one of the understatements of the season.
Some tandems defy convention on appearance alone. Last month's wild-card pairing of George Bastl and Dustin Brown felt like Grizzly Adams meets Bob Marley.
Swiss Bastl, thickly bearded and best known for upsetting Pete Sampras in the second round at Wimbledon in 2002, and Brown, a Jamaican with a flowing mane of dreadlocks, rode their hirsuteness to the semifinals.
Pairings can be calculated or haphazard, as when two players without partners meet at the tournament's sign-in area and join up on the spot. Americans Abigail Spears and Jill Craybas decided to play together at the start of the 2010 season while sightseeing on a bullet train in Japan last fall.
There can be all manner of intermediaries. Girlfriends, agents and coaches have all been known to bring two players together.
Resurgent Mardy Fish, who this year is dividing his time between singles and doubles with specialist Mark Knowles of the Bahamas, says that the partnership was abetted because "our wives are good friends."
Sometimes pairings thrown together by convenience or chance pay big dividends. Look no further than the unlikely and untested combination of 5-5 Vania King of the USA and 5-11 Yaroslava Shvedova of Kazakhstan.
King's normal partner, Anna-Lena Groenefeld, was out with a foot injury, so King agreed to play with Shvedova for the grass-court season. They had never played together.
Three tournaments later, they were Wimbledon champions.
"Before the grass season, she didn't have anyone, so she answered yes to me," Shvedova says with a chuckle of her timely arrangement with King.
King says off-court camaraderie contributed to the instant chemistry, which propelled them past Elena Vesnina and Vera Zvonareva 7-6 (8-6), 6-2 in the All-England Club final.
"You never know how it's going to work out until you get on the court," the 21-year-old from Long Beach, Calif., says. "But we wouldn't try to play together if we didn't think it would go well."
Beginners' luck? Maybe. But new isn't always good.
A fresh look didn't help Rafael Nadal and Novak Djokovic, who became the first players ranked Nos. 1 and 2 to play doubles together since No. 1 Jimmy Connors and No. 2 Arthur Ashe in 1976. The Spaniard and Serb lost in the first round at Toronto this month to unheralded Canadians Vasek Pospisil and Milos Raonic, proving that chemistry can be elusive even among the most gifted players.
More often than not, a pairing comes down to complementary skills, friendship and mutually agreeable priorities.
"I like playing with Sam because there is no pressure," Isner says of his friend, Sam Querrey, with whom he has played in 2010. "With doubles-only guys, there is a lot of pressure to perform."
Doubles, by its nature, crams the concept of teamwork into an individualistic sport, often with a shared sense of pleasure at distributing the pressure and workload.
Still, almost every player has horror stories of pairings gone awry. Lisa Raymond recalls one partner she declined to name ripping ball kids and mistreating transportation volunteers.
"It was almost like I was nervous the whole time," says the 37-year-old American, who owns 70 WTA Tour doubles titles and once topped the rankings. "That was an ugly six months."
The USA's Spears recoiled at one trash-talking partner whose aggressive rants "backfired almost every single time."
"I'm sure we've all had experiences where (a partner is) screaming at you during the match," King says with a scowl.
Autumn 'mating' season
If doubles has a mating season, it's autumn. This is tennis' version of speed dating, where eyes wander and potential partners are sized up for their skills (big serve? quick at the net?), personality traits (chest-thumper? peacekeeper?) or level of commitment.
"No one is putting out fliers or putting up notices in the locker room," Bob Bryan says. "It's really quiet. But people start whispering around."
Last year was particularly chaotic on the men's side, with a number of established tandems breaking up. Among those that split were top-10 doubles teams Max Mirnyi and Andy Ram; Knowles and Mahesh Bhupathi; and Brazilians Marcelo Melo and Andre Sa.
While doubles specialists usually go to great lengths to vet potential partners or jockey for the best fit, occasional pairings can arise so randomly that even the participants are caught unaware.
At an event in Belgrade, Serbia, last year, Southern California's Querrey scanned the draw and saw his name next to Sergio Roitman of Argentina — not as his opponent, but as his doubles partner.
"He came up to me, extended his hand and said, 'Hi, I'm Sergio,' " recalls Querrey, 22, still chuckling at the memory. "I'd never met the guy." Needless to say, the partnership didn't last (but they did play).
Many partnerships are based on a common foundation. Nationality, language or place in the tennis hierarchy is a natural bond. In the case of the Bryans and Serena and Venus Williams, it's as basic as genetic code.
The Williams sisters have 12 doubles majors and two Olympic gold medals, and the Bryans became the winningest team in men's history in July with their record 62nd ATP Tour title.
Bob Bryan says the ability to ride out rough patches is why he and Mike have lasted and had success.
"There's not a lot of teams that have stuck it out for more than two years, even on the men's side," says Bob, 32, who counts eight majors among his cache of 64 career titles. "There's always that finger pointing in a tough stretch. You lose some matches, and it's never your fault. Your partner could always have done something better. You go a few weeks without a win, and guys start looking elsewhere. Sometimes you need four to five tournaments to get a rhythm. Mike and I haven't had a lot of those stretches, but if we did, we'd stick it out."
Feelings can get hurt
Which is to say, Dr. Phil would have a field day counseling doubles partners.
As in any partnership, emotions, commitment and money can get in the way. Doubles is not immune to communication breakdowns, misunderstandings and hurt feelings.
Sometimes even the best partnerships can't survive, as when Liezel Huber and Cara Black— the top-ranked team at the time — split up in April. And it can turn downright chilly, as it did for the two women, who were barely on speaking terms after the dissolution.
Sometimes, breakups can serve as competitive fuel.
When Canada's six-time major champ Daniel Nestor told then-longtime partner Knowles that he wanted a change in the spring of 2007, the two icily stormed their way to a first French Open title.
Nestor, who is ranked No. 2 with Nenad Zimonjic of Serbia, says he regrets the timing of his decision and wishes he had waited until later in the season to break the news.
"I jumped the gun a little bit," the 37-year-old says. "Unfortunately, it took a toll on our friendship."
Moodie is another who has earned a reputation for his commitment issues.
The 31-year-old South African parted ways with Stephen Huss of Australia after winning Wimbledon in 2005 and dumped Dick Norman of Belgium at the end of last year after reaching the French Open final and Wimbledon semifinals.
"I didn't understand the decision at all," Norman, 39, says.
Their separation ended this spring, when the two decided to team up again and reached the semifinals at Wimbledon for a second consecutive year.
"I get stale quickly," 6-5 Moodie says. "I hope I'm not making too many enemies."
Many don't worry about feelings, treating the partnerships like a business. If they play well on court, it doesn't matter if they don't fraternize off it.
Gender stereotypes pop up when it comes to the musical chairs of doubles, and emotions cross both sides of the aisle.
"I think we are a little more practical, and we just get over things," veteran Leander Paes of India says. "Women are more emotional, but in some ways that's great. They are a lot more refined than we are."
It's also a fact of tour life.
"There's definitely a lot of drama that goes on in doubles," says 23-year-old American Carly Gullickson. "If someone is not going to get in (to an event based on their ranking), they'll sign up with someone else. It's business. You have to do what you have to do. Sometimes feelings get hurt."
As with any joint endeavor, commitment can waver, even with success.
Despite wining their first Grand Slam crown at Wimbledon in July, occasional partners Jurgen Melzer and Philipp Petzschner hardly sounded hitched.
"I think we could play awhile," Germany's Petzschner says. "But you never know."