Zoe

"Huh, Mark? Whaddya doin' on the floor?" Zoe asked, her eyes half shut sleepily. Your older sister was not a morning person. From your vantage point on the floor, your eyes were drawn to the package straining to burst out of her white panties.

"Morning Zoe." You decided to spare her the guilt. It didn't really hurt you. You hop back up and remembered you were naked and cupped your hands to hide your genitals.

"Oh, were you gonna shower? Then... let's do it together." Before you could protest Zoe pulled her T-shirt off. Her ginormous breasts flopped out, perfectly shaped despite their immense size and topped with delicious nipples. "Okay..." You blurted out.

"Yay! We've not showered together in so long!" For good reason, you think, as her panties came off. Gods she was so hot, you thought, and your cock stiffened to full rigidity.

Zoe stepped under the shower water and you joined. She insisted on soaping you up, and being the younger and smaller sibling, you did not protest.

"You're so small and cute, Mark. So... small?" Her fingers brushed against your erection. "I can wash that myself, sis." The touch made you flinch but you backed into something hard that poked your butt instead. You turned around and your cocks touched.

"This is just... just morning wood!"

"Yes, it's just a natural reaction." Zoe agreed. An akward silence ensued while you were both staring at the throbbing cocks. "Umm... Mark, you must make sure to wash your penis... why don't I show you the correct method?"

"Y-yeah, sure." Zoe grabbed your shaft and stroked it.

"Just like that, you need to make sure to keep it clean." She was honestly cleaning it thoroughly, but soon dropped the excuse and was clearly just giving you a soapy handjob.

"Can I, um, practice washing with your penis?"

"O-of course."

Zoe's cock was so thick you couldn't even close your grip around it. You marvelled at the hardness and sheer weight of it. Both of you had the same idea and brought both the cocks up close so that the tips rubbed together. This was an extra layer of stimulation that made your toes curl. It felt worlds better than jerking it yourself.

"I'm going to cum."

"Me too."

For some reason you looked up as you were cumming and found Zoe staring right back. You both lock eyes as the climax scrambled your brain. Hot semen exploded from the tip of your cock. It was too much to bear and you slumped onto the floor.

"That was crazy good." Zoe said, her cock still mostly hard. "God, what have we done. I didn't... I didn't **** you, did I?"

"No! I liked it too."

"That's great. But don't tell mom okay? She would gut me."