Relationships can be unpredictable. Romantic relationships even more so. And if it's one in Bollywood, you'd never really know what to expect the morning after. If being friends with your ex was a big no-no in your rulebook for love, you may want to consider bending those rules a little. At least, that's what our Bollywood girls and boys seem only too happy to do, as long as it's for work.

Here's what seems like Bollywood's oldest love story. Ranbir Kapoor walked into the industry hand-in-hand with Deepika Padukone in 2008. His first film flopped and hers made her a household name overnight. But soon the tables turned. Ranbir Kapoor became one of the hottest stars in tinsel town as well as a much sought after playboy. Much to Deepika's discomfort, he was linked with virtually every girl he spoke to, making the much-in-love girlfriend insecure and unsettled. The final straw in breaking-up this one-year-old relationship was his onscreen chemistry with co-star Katrina Kaif.

The Ranbir-Kat jodi was an immediate hit. And, as his career soared, his love life took a huge dip. The break-up wasn't pretty, with Deepika calling Ranbir a 'cheater' on national television. However after this much history and mystery, the two have now agreed to work together in Ayaan Mukherjee's Yeh Jawani Hai Diwani. "They have a very amiable equation, so I knew there would never be a problem," Ayaan was quoted saying.

With Ranbir dating a thousand women since, and Deepika finding solace in a certain 'prince' of good times, the two seem to have now let bygones be bygones. "I have always wanted to work with Ranbir again," says Deepika, proving that she's not one to let matters of the heart come in the way of her movies. After all, who would be foolish enough to let go of an opportunity to be cast opposite Bollywood's youngest and most popular superstar in the making. She recently even invited him over for her housewarming party. Smart girl.

She is the queen of item numbers and he is the king of blockbusters. But even before Katrina Kaif became Sheila and Salman Khan turned Dabangg, the two were pretty much inseparable for many reasons. They may have never officially declared their love for each other, but Kat's baby steps in Bollywood were all thanks to her good friend and guide Sallu. They've known each other for almost nine years, where questions about their relationship status dominated headlines more often than not. However, apparently his possessive ways and her independent nature could never really find a way to co-exist.

Last year, Salman announced his break-up with Kat during a television interview, followed by a much pubic breakdown by Kat during a press conference. But there was no room or time for any bad blood. He needed her item queen act for his films and she could never really do without this Khan by her side. "Salman and I have always been good friends and that can never change," Katrina told Mid-day. The good friends are now on their way to making a film that may well go on to becoming one of 2012's biggest hits.

And though we can never imagine Sallu getting back to working with any of his other exes (mainly Aishwarya Rai Bachchan), we guess it pays to be best buds with sexy Sheila. Their so-called relationship lasted probably just bit longer than the name of their next film. Nevertheless, let's not forget that this now-on, now-off couple gave us Kaminey.

She as the Marathi Mulgi and he as the stammering Guddu did give us some pretty precious on-screen moments to hang on to. Unfortunately, the same cannot be said for the two off screen. Shahid Kapoor and Priyanka Chopra's fights made more news than their films. Their chemistry was pretty apparent at Karan Johar's television show, where the two unabashedly flirted with each other. However, after one too many alleged make-ups and break-ups Shahid and Priyanka apparently called it quits early this year.

But, soon after, came the announcement of them having signed their second film together. So whatever their off-screen equation might be, this is one couple that we think may manage deliver well on-screen. It was the one of longest relationships that Bollywood has seen, and a break-up that stumped many within the industry. But Shahid and Kareena Kapoor have always been civilised about their separation.

She fell for Chhote Nawab during the shoot of Omkara, leaving Shahid heartbroken, even if just for a bit. However, post the break-up came their first and one of the biggest hits of their careers Jab We Met. "Shahid and I can never have any bad blood," says Kareena. Probably why she wouldn't mind if he was part of the sequel to Once Upon a time in Mumbaai. And though there is hardly a chance that they would star opposite each other, we would like to see that Jab We Met spark once again!