TORONTO -- Walking down the mean streets of a (Toronto soundstage) ghetto, "Four Brothers" from different mothers pick apart their surroundings, and each other, with equal helpings of love and loyalty. Is it real or a movie? The truth is, it's a little of both.

For "Boyz N the Hood" director John Singleton's upcoming movie, Tyrese, Mark Wahlberg, Andre 3000 and "Troy" star Garrett Hedlund play so-called brothers whose bond is much thicker than their blood. (Click here to watch exclusive clips from the film on Overdrive.) When their adoptive mother is murdered, the men return to their old neighborhood to avenge her death. On a recent visit to the Canadian set (doubling for Detroit), the stars discussed unbreakable bonds, both onscreen and off.

"This is the first time I've done something that's kind of street since 'Basketball Diaries' or 'Fear,' " said Wahlberg, who plays the eldest brother in the film. "This time, at least, it's for a reason -- hopefully, people will root for my character in 'Four Brothers,' instead of wanting to see me die at the end."

Wahlberg might just get his wish, as the film's dramatic storyline makes a strong play for viewers' heartstrings. "The mother gets killed, which brings all of them back," recounted the 20-year-old Hedlund. "These boys were adopted, they went from foster house to foster house when they were younger. This lady, Evelyn Mercer, couldn't find a house for them, because they were all sort of misfits -- these were the only four she couldn't find a home for, so she took them in as her own and adopted them. So they became brothers that way, definitely not by blood."

Photos: Check out photos from the set of "Four Brothers"

"We were adopted when we were very small," added Andre, the actor and world-famous Outkast frontman. "We pretty much did grow up in the same culture. Our mom was a neighborhood helpful person, and she saw that these kids needed help."

On the set, each star has had a role assigned to them that plays to their personal strengths. "I'm not the thinker of the family," laughed Wahlberg, who looks more bulked-up than ever. "I'm the doer. I've got two of the other three brothers following me around; Andre's character, Jeremiah, is the thinker of the family, he's supposed to be responsible. We drag him right down into the [gutter] with us."

"I'm the one playing the singer in the movie," Hedlund said ironically -- because he's the only star of the film who hasn't been a recording star in real life. "He moved out to New York to sort of pursue his rock career ... The character's name is Jack, he's the youngest brother, he takes all the [abuse]."

As the four have passed countless Canadian hours both on and off the set, they've found themselves forming a bond similarly fueled by brotherly teasing.

"It's loose; we've been together for so long that all we do is snap on each other," Wahlberg said, grinning mischievously. "[Hedlund] gets it, but he's an easy target -- he's got a very large head. They used to call me 'Big Head,' and then when I finally saw someone with a much bigger head than me, I was happy. Anytime I'm photographed or anything, I want Garrett beside me, so my head looks small."

Watch exclusive clips from "Four Brothers" and hear what Andre Benjamin and director John Singleton have to say about vengeance, justice and filmmaking ... on Overdrive.

"Off set we're like real brothers, we're jawing each other, we're jawing each other's clothes," Andre agreed. "We know that we're in character clothes, and you may hate your clothes, but you're still jawing them. Man, we don't stay off each other; it's like high school. It's really like brothers."

The fun has even spread to the chairs they sit in between takes, where the inscribed names have been altered to fit their personalities. "We did a little custom work for Garrett's chair," Tyrese said, giving an impromptu furniture tour. "So, that's Garrett 'Big Head' Hedlund. This is Mark's chair [which simply said 'Mark Wahlberg'], he stuck to the basics ... and, your boy, I'm right here, look!" he said, pointing to a chair that read, "Tyrese 'Always Expect the Unexpected' Watts Boy."

"See?" he said of his heritage, having grown up in the notorious California ghetto. "The 'hood is on the map, baby. If they don't know, they're about to know."

It's just one lesson these "Four Brothers" hope to teach people as they roll into theaters August 12.

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