This is a true story from when I was dating my wife when I was 21. The names have been changed to protect the individuals.
A gentle summer breeze drifted through the window into the dark bedroom. Scott listened to the quiet breathing of his girlfriend, Kara, beside him and on the far side of the bed, her sister, Grace. It had been the sleeping arrangement for the past few nights now, ever since Grace had lost her place. It didn't bother Scott at first but a few nights without any private time with his lover, he was beginning to feel the strain. It didn't help that her sister was practically as gorgeous as she was. Grace kept her hair short, in contrast to Kara's long thick hair. She wasn't as tan as Kara and was a bit curvier but that only added to her attractiveness. And to top it all off both had an impressive rack, though Grace was slightly smaller. He learned this after 'accidentally' seeing her change.
Just thinking about it was making his large cock swell and he shifted slowly to free himself from Kara. He quickly reached into his pajama pants and removed his stiffening member. He began to stroke slowly, thinking about the two girls beside him. Before he knew it his pace quickened, and as a result so did his movements. Kara stirred beside him, rolling over as her eyes began to flutter open.
"Scott?" She whispered. Then her eyes spotted his hard cock.
"I was just-" He stammered out but she just put a hand up to his mouth and stopped him. She rolled in and gave him a deep kiss. They held it for a moment until she pulled away slowly. He felt like he was going to explode, when she reached down and took his cock into her own hand and began to stroke it. She glanced over her shoulder to check on her sister before flashing him a smile and sliding down to his junk.
Scott bit his tongue to keep from calling out as Kara slid his throbbing member into her mouth. She started of slow, working the rest with her hand as he felt her tongue work across him in her mouth. She popped him out of her mouth for only a moment to catch her breath before sliding him back in. She grasped either side of his hips and pulled herself deeper onto his penis. After a few tries, her nose tapped his stomach as she took his entire length.
Scott lost it. Before he could utter a sound he exploded down her throat. She gagged for a second, pulling back slightly but not letting his cock slide out as it spurted an almost entire week's worth of built up cum inside her. When he was finally done, she worked his cock a minute longer, draining him of any remaining cum. Finally she pulled her head back and wiped the remains off of her mouth and moved back beside Scott. Grace stirred slightly but didn't wake.
Kara pulled Scott for a kiss and the two swapped juices as they made out. His hands slipped up her night shirt and he gave her breast a good squeeze before playing with her nipple. She let out a quick gasp before adjusting so he could take her breast in his mouth while his hand toyed with the other. She grabbed the back of his head and moaned quietly as her hips writhed from the pleasure. His free hand wandered down across her smooth belly before sliding into her pajamas and rubbing her wet pussy.
Kara bit her lip as she tried to keep her pleased moans quiet. He began fingering her vigorously as he gently massaged her sensitive nipples with his tongue and fingers. It wasn't long before he felt her pussy tighten and she buried her face in the pillows to muffle her cries as she orgasmed beside him.
When she was done she was breathing heavily, gazing into his eyes. She pulled his hand out from between her legs and brought his fingers up to her mouth, sucking her cum from them. Grace let out a soft sigh as she rolled over to face them. She had yet to awaken but the two sat quietly for a moment, just in case. After she didn't stir, Kara turned back to look at Scott.
"You're still hard." A coy smile formed on her lips as she looked at him.
"How can I not be, with you right here?" He gave her a quick kiss before she gave one last glance at her sister. She turned back to him returned the kiss.
"Well I guess since it's my fault I could try to do something about it." She slowly removed her bottoms and Scott was quick to do the same. She moved to straddle him, guiding his still rock hard member to her entrance. She lowered herself nice and slow, giving her pussy a chance to stretch. If he hadn't already it would have been enough to make Scott explode.