It had been awhile, maybe as long as a year, since she'd seen Billy's cock. She wondered if it had grown. Was it as big as Jimmy's? Had he grown more hair on his crotch and did his balls hang down heavily, like Jimmy's?

Her virgin cunt twitched and felt hot and heavy between her legs. On an impulse she pushed the bathroom door open slightly and peeked inside.

Billy chose that moment to shut off the shower and step out into her line of vision. He didn't see her as he reached for a towel.

She saw all of him, however. Her eyes widened as she gazed at his prick. It was as big as Jimmy's and he had indeed grown more hair on not only his crotch, but on his balls too.

The horny teenager held her breath. Both her brothers were turning into studs. How exciting!

Billy dried his crotch and hummed a tune as he examined his face in the mirror over the sink. She squinted to see into the room. He was looking for signs of a beard on his chin. She almost giggled.

But what drew her attention was his prick. It was long and thick and dark pink. She became so engrossed in his cock she failed to see him spy her in the hallway.

"I know you're out there," he said. "What the fuck do you think you're doing, Sis?"

When the door was pulled open, she fell forward, landing against the naked boy. She was too stunned to speak, but his cock stabbed her hip and they both sprang back.

He quickly wound the towel around his waist, hiding his prick from her probing eyes. "Hey, get out," he said.

But Penny became bolder and grabbed the towel, yanking it down. "I like to see it," she said.

"Jesus Sis, you're crazy," he said, trying to cover himself. "Do you know what you're doing?" He jerked the towel from her hand and tried unsuccessfully to tie it around his waist.

"Let me see," she giggled, grabbing the towel and pushing it behind her back. "You used to let me see your thing. Why can't I see it now?"