Sirius eyes his little brother as much as he can manage during the match while still keeping his focus on the Slytherin chasers.
James is busy being a ponce high above the pitch, doing his job as much as he is lollygagging. Regulus has a strange strategy where he stays closer to the ground.
Sirius has just blocked three Slytherin attempts to score when he sees Regulus spike up into the air, broomstick parallel with one of the viewing towers. James jumps into action seconds later and then it’s a race for the snitch.
Sirius keeps one eye on Kleppburn who’s taking the discovery of the snitch as an opportunity to score (which fails of course) as he watches the tussle that’s commenced between the Seekers.
He can see James’ hand surrounding the snitch when a horrid gasp breaks across the crowd. His eyes snap down to the falling streak of green robes and black hair plummeting toward the grass.
He’s moving before he even realizes, but he’s too late to do anything as Regulus gets momentary control before slamming sideways into the baseboards of the pitch.
He lays there in a gasping heap as Sirius jumps from his broom ten feet in the air. He rushes over to his little brother and takes a close look. He doesn’t see any clear injuries but he does see Regulus struggling to breathe.
“Reggie,” he says quickly, “Reg, what’s wrong?”
Regulus only heaves in response, a terrifying rattle the only sound Sirius can actively hear (the ref and several teammates on both teams can be heard distantly in the background). The younger brother lies almost completely still except for his heaving breaths.
“Regulus!”
“S-Shut,” a withering gasp, “u-up.”
“Oh, Reggie,” Sirius sighs, “you’re okay.”
Regulus sits up and coughs, swiping his black hair away from his face.
“Reggie, how many fingers am I holding up?” Sirius holds three fingers in Regulus’ face as the ref comes closer.
“Piss off. I don’t have a concussion, clown.” Regulus stands with the help of the referee and glares at Sirius. He holds his chest with a pained look. “Go gloat about your win somewhere else.”
“Huh?” Sirius asks dumbly.
James comes up and claps Sirius on the shoulder. “I caught the snitch, mate. ‘Member?”
“Oh, yeah! Nice one, mate!”
Regulus scoffs and walks off the pitch and into one of the changing rooms.