BURBANK, Calif. ( TheStreet) -- No longer children but not yet teenagers, "tweens" are now considered a powerful consumer demographic in their own right. Between the ages of 8 to 12, kids begin to develop into independent consumers: spending their own allowance money and showing specific brand preferences when shopping with Mom or Dad. Walt Disney ( DIS) has been especially successful appealing to tween girls. The company helped launch the careers of actress Miley Cyrus and pop stars the Jonas Brothers, turning them into international brands available on everything from backpacks to snacks. But Burbank, Calif.-based Disney hasn't had a comparable hit with tween boys, which might help explain this week's announcement that it will buy Marvel Entertainment ( MVL), home of iconic male-oriented characters such as Spider-Man and The Incredible Hulk. The Disney marketing machine has convinced tween girls to spend millions on merchandise from Cyrus's show, Hannah Montana; it can probably spin superheroes into a massive new revenue stream. But there's no reason small companies can't get into the boy business, too. Tween boys have been somewhat overlooked compared to girls. Companies that understand how to appeal to their interests have the advantage of relatively few competitors. According to youth marketing company Alloy Media + Marketing, tweens spend $51 billion each year, with their families kicking in an additional $170 billion. To get in on that market, you must understand how tween boys think, says Adriann Fonstein, consumer strategist for AMP Agency, a unit of Alloy. "For them, life is about play. They like silly, physical humor. You have to make them feel like they're in on the joke."