HAMPTON, Ga. —The Busch brothers are banging on the Allisons’ rear bumper for the top spot on the list of NASCAR Cup Series wins by siblings. On Sunday, however, the sibling rivalry between Kurt and Kyle Busch was the story. Thanks to Kurt’s win over runner-up Kyle at Atlanta Motor Speedway, each has two wins in the four Cup races featuring one-two finishes by the brothers. That was a cause for celebration for older brother Kurt, who climbed out of his car and yelled, “Hell yeah, we beat Kyle!” It was a sore subject for Kyle. Kurt said his younger brother dropped by victory lane to “do the Kyle Busch grumpy.” Neither likes losing to the other. It may be especially difficult for Kyle, even though he’s had more NASCAR success. “It’s a little-brother syndrome,” Kurt said. “I’m an older brother. I don’t know what it is to be the …