Matt restrains himself... barely

Slopping sunscreen on his sister shouldn't have been hard. She was his sister, for Pete's sake. They'd spent their lives squabbling over who got the odd piece of candy in the bag or who was taking too long in the bathroom.

But looking at his sister's naked ass gave Matt ideas he didn't want to contemplate... at the same time as he very much wanted to contemplate Karen's butt.

He stroked on the sunscreen, starting with her back, then moving to her calves and thighs. Finally, he squirted a glob of sunscreen into his hands and turned to her ass.

She had a really great ass. Countless hours in the saddle, riding horses, had toned her body and gave her muscles Matt could only imagine tightening around his dick.

He took a deep breath, rubbed his hands together so he wouldn't freeze her but with the cold sunscreen, and started rubbing.

"Thanks for warming it up," Karen said.

"Your ass or the sunscreen." He regretted the words the second they left his mouth... he was flirting with his sister. How sick was that?

"Both, I guess. But I was talking about the sunscreen."

And she was flirting back.

His dick was harder than it had ever been. He was stroking a pretty girl's naked ass. He'd imagined how it would feel, how it would smell but this was better than he'd imagined... except it was his sister.

The temptation to stick his hand into his shorts and jerk off... after all, Karen was face-down on the lounger and couldn't see what he was doing, was almost more than he could endure.

He pulled his hands away and wiped them down with a towel. "Sorry, Karen. I think I'd better stop there. I hadn't realized how sexy you are when I started and, well, you are my sister."

"And you are a sick puppy," Karen told him. She pushed herself up from the lounge chair and Matt could see her pulse beating fast in her neck, her nipples puckered through the thin fabric of her bikini top. "Maybe we should get started with trig. That should get your mind out of the gutter."

Oh, yeah. Thinking about Ms. Chadra would sure do that. Not.