'Brothers' Stars Tobey Maguire, Natalie Portman Talk 'Growing Up Together'

'Knowing someone for that long is a great history to have when you're playing husband and wife,' Portman tells MTV News.

At the center of "Brothers" is one seriously twisted love triangle. When Sam Cahill (Tobey Maguire) heads off to war in Afghanistan and is thought to be killed in action, his wife, Grace (Natalie Portman), starts getting cozy with her ne'er-do-well brother-in-law Tommy (Jake Gyllenhaal). Things get ugly when Sam is rescued, suffers from some bug-eyed post-traumatic stress disorder and does not take a liking to his bro's lovey-dovey rapport with his gal.

In short, this trio's various relationships go from adoring to strained to infuriated and back again. But these three Hollywood stars have known each other for years, as they explained to MTV News, and those connections helped inform their performances in front of the camera.

"I've known Tobey since I was 14 years old," Portman said. "It was kind of amazing to step in and already have that history of growing up together. Just knowing someone for that long is a great history to have when you're walking on set and playing husband and wife."

Indeed, in early scenes where Sam and Grace are giving their young daughter a bath or when the couple share their final hours together before his Marine unit ships off for the battlefield, Maguire and Portman display an easy rapport that seems as much a result of professional skill as it is personal affection.

"I met her at a screening of a movie -- I can't remember what the movie was -- but I remember after the movie, we were talking about the film and there were some criticisms that I had, and Natalie goes, 'Wait a second, you don't know the three-block rule?' " Maguire told us. "And I go, 'The three-block rule?' And she goes, 'You don't talk about the film until you're three blocks away!' So Natalie, when she was 14, taught me about the three-block rule."

Onscreen in "Brothers" (out December 4), as quickly as Sam and Grace establish their rock-solid bond, he's seemingly taken out of the picture for good (he's thought to be killed when he's actually become a P.O.W.). Slowly, Grace grows closer to Tommy. For this relationship as well, Portman had a personal connection to draw from.

"I met Jake when I was 18, and he's been a dear friend for 10 years now," she said. "It's really wonderful to start with that level of familiarity. And also to see your buds do an incredible job up close, because you just know them socially, and then to see them flex their acting muscles to this level is really amazing."

Check out everything we've got on "Brothers."

For breaking news, celebrity columns, humor and more -- updated around the clock -- visit