Shaun and Christine stood together, toe-to-toe, buck naked in the shower. Their eyes were locked together, their chests rising and falling as they both breathed heavily, the water hot and steaming as it ran through their hair and coursed down their bodies. They were separated by inches that Shaun's cock threatened to bridge as he mentally struggled to control his arousal; all the while, he and Chris were locked into a showdown, a battle of wills - he wanted the shower to himself, and she stood pinned into the far corner, refusing to leave.
"Go on..." she whispered, expectantly. "What are you going to do?"
Oh, all the things Shaun wanted to do to her. He wanted to take her. He wanted to scoop her up in his arms and embrace her, softly and passionately. How he loved her, how he wanted her, how he wanted nought and nothing else but her.
But he couldn't. She was his sister. His foster-sister, his adoptive-sister, yes - but they were brother and sister in their hearts, they knew it and they couldn't deny it. Yet somehow that knowledge made their yearning all the sweeter, it made the tension all the more acute as they yearned for the forbidden, they both wanted what they couldn't have...
Shaun heaved a sigh, and he smiled. He leaned forward, held her hands, and he placed a single, delicate kiss upon her forehead. He lingered there, and she shut her eyes against the thrill of it, the tingle that started at his lips and coursed up and down her entire body; then he moved back, the smile still there.
"Love ya, sis," he told her. And then he was going, he was leaving, he was getting out of the shower.
She was at once bitterly disappointed and immensely relieved. He wouldn't do it. He wasn't going to do anything. She had left the door open, as it were; she had given him an opportunity to do something, to have a go, to do with her as he pleased. She had even managed to do it subtly, seductively, teasingly - she hadn't spread her legs and cried "Take me now!" or anything like that, she had done it coyly, enough so that he probably couldn't be sure that she had even given him the chance.
And as she watched him towel off, she smiled. His response - that single, sweet kiss upon her forehead - was so like him. It was probably the best outcome she could have hoped for, possibly even more satisfying than if they had touched each other and gotten together.
He turned, and looked at her, and saw her smiling at him. He smiled back and shot her a wink.
"I guess I won," she said, simply.
"Yep," he grinned. "You win, little sister."
She laughed as he started to leave. "I'm still older than you, little brother!" she called after him.
"Yeah, well give me a few months, I'll try to catch up."
* * *
Before they knew it, it was Friday, and graduation was upon them. They all sat in the high school auditorium with their peers and their families; Mrs Whitmire handed out a few awards and said a few grudgingly nice things about the graduating class, and then they lined up to receive their diplomas.
Christine Cleary stepped up first, taking her diploma from Mrs Whitmire with a smile and a hug. Then it was Shaun Cleary's turn, and Mrs Whitmire fixed him with a cooler, grudging look of wary congratulations as she gave him the diploma; as he took it from her, he moved quickly past her defences and enveloped her in a great big hug, picking her up and twirling her around once or twice as well, to the general merriment of all bar Mrs Whitmire - who had to steady herself before handing over the next diploma.
Mortar-board hats were flung and cheers erupted as it was all done. Bill and Therese, ever the proud parents, congratulated their children and took them home to prepare for their formal dinner and dance (otherwise known in certain parts of the world as "the prom").
Shaun was ready first, and he sauntered into the living room to model his suit for his parents: a brilliant white affair, white jacket with tails, white shirt, white tie, white pants, white shoes and - to complete the package - a white-tipped cane and a white top hat, which was trimmed with a white ribbon.
"Don't you drop your dinner on that, boy," Therese warned him.
"I won't, thanks mum," Shaun groaned, rolling his eyes.
"You're looking pretty dapper there, my son," Bill approved. "You'll doubtless drive the young ladies wild..."
"As always," Shaun grinned, joking-but-not-really.
"Your parents would have been so proud of you, Shaun," Therese told him, referring to his biological parents. She started to tear up, so Shaun went in and met them both for a hug, and Therese tried valiantly not to weep on his white suit.
"When you're ready..." Chris said, behind them. They had missed her glamorous stroll down the stairs, and saw her standing impatiently with hands-on-hips. She was beautiful in a softly-coloured lemon dress: draping low to her heels, generously cut in front so as not to hide the assets, and as she spun she revealed a low-cut back extending nearly as far as her shapely bottom.
"Oh dear," said Bill, his heart clearly breaking. "Who said my little girl could grow up so fast?"