Just watch for now

"I think I'll just watch," you reply after a moment's thought, "I didn't bring any workout clothes." The idea of working out has never really appealed to you, but you are more than willing to watch an attractive woman exercise, especially if they're wearing a semi-revealing outfit like Janis'.

"Oh, okay," Janis shrugs with a smile as she brushes her blonde hair away from her eyes, "I might need you to help with some of the floor work though," she warns you as she turns away again.

"Not a problem," you agree, having helped her out with two-person routines all through her gymnastics' career. Back in high school, Janis always tried to convince you to take up the sport, commenting how good you were at being her partner; but you always refused: you weren't about to let anyone from high school see you in a leotard. You lean back against the door frame to watch your older sister as she continues to work out, your eyes running over her body as she continues to stretch and bend in positions that almost seem designed to tease you. You try not to let your eyes linger on your sister's pelvis too much but the enticing show that her leotard is making of her stretches keeps drawing your eyes.

"Okay, John, are you ready to help me?" Janis asks, slightly breathless from the rapid routine of stretches, as she moves to stand in the center of the room with her back to you.

"Sure," you agree, your hand dropping down to quickly readjust your burgeoning erection in your pants. "What do you want me to do?" you ask, as you step up behind her.

"Just spot me as I go through the routine," she tells you, "I haven't done some of these moves in a few years and I might be a little rusty."

Without saying anything more, Janis slowly bends over backwards, her back arching as her arms stretch over her head until her hands touch the floor. Her body arches completely as she slowly lifts her one foot and then the other off the floor, as she goes into a handstand. Since you are standing behind her as she performs this move, her face is nearly even with your crotch as she balances on her hands. She keeps her legs slightly parted to help with her balance, putting the stretched crotch of her leotard right before your eyes, your hands outstretched to hover near her waist in case she loses her balance. You know that you should be concentrating on what Janis is doing, but the proximity of her crotch to your face is filling your head with less than brotherly thoughts.

"Uh, John," Janis' voice breaks into your reverie, your cheeks burning in embarrassment as you tear your eyes away from her crotch, glancing down at her face only to see her eyes fixed on the rather large bulge in your pants.

"Oh... sorry, Jan," You stammer, stepping away from her, turning your hips so that your erection won't be quite so noticeable as she lowers her legs back to the floor before turning to face you.

"Is that... Did I..." your older sister stammers, her cheeks flushed a deep red that probably matches your blush. "Did I cause that?" she finally manages to ask.