I've known some pretty bad kids growing up, and if there's one thing I've noticed from personal experience it's that the sooner you address it the better. Yeah, he's young and may grow out of it, but on the off chance that he doesn't I can only imagine it getting worse with you and your folks having a much harder time mending the issue as time goes on. Here's some examples of kids I knew growing up, and where they are now:
Friend 1 (at age 13): Constantly skipped class and would throw violent temper tantrums not unlike your brother. His parents couldn't seem to figure out a way to handle him. Now 21, he is serving four years in prison for serial arson.
Friend 2 (at age 15): Underage drinker and pathological liar who would constantly steal money from her parents and hook up with men of legal drinking age to supply her with alcohol and "party," among other things. Mother was easily intimidated by her, and her father continued to treat her like his little princess, perhaps due to denial. Now 26, she's a meth addict who's been in and out of jail more times than I can count, still living at home.
Friend 3 (at age 14): Spoiled brat who couldn't even imagine a world which doesn't revolve around him. A spiteful SOB who stole from friends (myself included) and family, joined a small gang that was responsible for jumping and robbing several kids around town, and only went to school to fuck with teachers and be a complete dick. His parents gave up on trying to straighten him out, and continued to pamper him for as long as I can remember. He'd now be 24, but he was shot and killed in an alley not far from where we grew up over petty theft.
It's sad, but I can actually think of at least three more personal examples, but I think you get the point.
I don't believe beating the kid is the best option. Instead I'd suggest taking his door off the hinges and limiting him all the luxuries that I'm sure he takes for granted. Cut his food in half and eliminate snacks altogether; rig it so that when he showers there is no hot water; does he have a TV in his room with cable? Not anymore; Internet access? LOL, no.
In fact, next time he's out of the house just go in his room and start packing his shit up in boxes and put it in the basement. When he comes home all he'll have in his room is his bed, clothes and basic essentials. If he wants to act like an unruly inmate, then he can fucking live like one. I mean it too, give him an actual "prison sentence." Let's say one month under these conditions, no exceptions. He can beg and cry, but don't give in. Fuck that noise.
If after a month of that nothing changes or he gets worse, then yeah I'd be looking for a professional, because today you can't just beat up on kids without expecting to catch a case.