Unlike games for girls, games for boys involve more action, building things, the great outdoors, and competition. Be prepared to handle "band-aid and neosporin" injuries and remember that boys will be boys!
1. Good old-fashioned rough-housing Nice thing about this is you simply order the boys outside, keep a watch on them, and have the band-aids and neosporin handy for when one of them gets hurt. They love back-yard football and wrestling, but typically one child is bigger or faster, which leads to one of them getting hurt. And they don't want to stop rough-housing until someone DOES get hurt. You can attempt to call it off beforehand, but it's oftentimes easier to let them get that energy out, even if someone ends up with a new knee scratch.
2. Outdoor Games Besides the great outdoor games for boys linked here, also remember 4-square, which requires nothing more than a kickball and a piece of chalk on the driveway. Two tennis racquets and a beach ball makes for a delightful game of "keep it in the air." That's the unofficial title for any game that has a light enough ball to bop into the air and count how many back-and-forths you can count up to. Families with boys will have an uncanny amount of balls in the garage. Tennis balls, baseballs, basketballs, softballs, golf balls, etc. With all these balls, you can easily make you own bocce ball game, game of catch, obstacle course involving using different "bats" to hit different balls.
3. Indoor Games It's raining or otherwise impossible to go outside. Not all games for boys require sweat and blood, thankfully. Another asset of most homes with boys is a plethora of board games and puzzles. In fact, they may have so many board games and puzzles that they've forgotten about one or two tucked away on a high shelf. Boys still enjoy Battleship,Checkers, many of them chess, and puzzles. You'll be impressed at how some older brothers will include the younger ones, or play younger-focused board games, to enable siblings to play. They may even have games that you had as a child that they don't know how to play. (That will make you feel old!)
4. Building Games Lots of boys enjoy building a fort or at least starting one. They may want it to become a hammer-and-nail project, but challenge them to build a fort with the toys and materials in their yard and garage (without power tools), or if you've asked the parents, maybe an old sheet or two.
A simple but entertaining game boys enjoy is "who can build the tallest." You have to monitor the building materials they use, and you may want to make this an outdoor project, but the concept is to build a tower of items and see who can get their tower to the highest point. You'll have to challenge shorter younger brothers to think creatively when they can't reach as high as the other boys, or you can say it's only fair to let them use a chair.
Dig around for the Tinker Toys, K'Nex, Lincoln Logs and Legos. These classics remain popular, even with some small pieces. If they've lost the instructions on how to build certain things, looking at ideas online--even without all the pieces--can still be fun and spark new ideas.