Joel was just finishing mowing his lawn when Lucille activated the Priapus Tool on him.
He went to the bedroom he shared with his 18 years old brother, Randy, 6 years older than him.
When he entered, Randy was kissing with his girlfriend, Katy, who Joel had a crush on. He tried to don't interrupt them and take some clothes for his shower, however Randy noticed him and angry yelled to him to go out, throwing a soda can to him.
Joel left his room and went directly to the bathroom. He took his clothes off and entered the shower cabin.
He was thinking about Katy, her gorgeous blonde hair, her wide hips and her prominent breast. As he was still thinking about her, his pubescent dick began to throb and get hard. In no time, he was rubbing and soaping his 3 inches erection.
He began to gasp as his libido began to grow. His hormonal levels were shooting up so fast, that he was losing balance. He leaned against the wall and slowly slid to the ground. When his butt touched the wet floor he shot his first load, nothing impressive considering his age but that was the starting point to his further development.
As he was still too horny, he didn't realize that his dick was slowly growing in his hands, each throbbing was pushing it a little longer and thicker. When it was too big for one hand, he instinctively used the other as well.
The water was still falling on his body when it began to pump up. His chest, shoulder, arms and legs were widening to the rhythm of his dick's throbbing. He was getting bigger and older so fast that he didn't notice his bigger frame in the shower. His feet, which got a size 15 during the process were now pushing the shower's entrance so he had to spread his meaty tree trunk legs, exposing his bigger balls which were now hanging low and resting on the wet floor. He shot his second load at that moment, a bigger and messier amount than the first one.
Randy stopped kissing Katy for a moment when he felt a huge urge to pee. He left her in the bedroom while he goes to the bathroom. As Joel forgot to close the bathroom, he came in ignoring his brother in the shower and began to pee. It wasn't unusual to him to pee while Joel was in, so can proudly show off his bigger manhood to him. However, this time he realized something was wrong when Joel made a deep grunt while showering. Randy looked from behind and immediately screamed when he saw an unknown guy intensely jacking off in the shower.
"Who the fuck are you?" Randy yelled at him, he was too surprised that he didn't have time to put his dick back inside his pants. Joel was a little dizzy, but he managed to stand up with his big feet on the wet floor. Randy was shocked when he realized that the guy looked almost exactly like him, except for the curly hair that just Joel had in his family. That's how he connected the dots and realized that this guy could be his little brother, Joel. "Joel?!" But Joel didn't answered and instead he shot his third load on his brother's exposed dick. "Shit! That's gross, asshole!"
What Randy didn't know and Joel didn't remember it's that the Priapus effect was contagious through sperm and unwittingly Randy was getting a hard on too.
"What the fuck?!" Randy shouted this his 8 inches pal fully hard. "I'm not gay, why are this turning me on?!!"
Joel had already stopped rubbing his manhood but his dick shot a fourth and last shot which fell in both his and Randy's chests. Hair began to spread there as they were going through a similar growth process. Randy's feet grown to catch up with Joel's big feet as Joel body hair grew and thickened on his arms, legs, armpits and crotch until they looked like twins.
Due to the strong growing hornyness on his body, Randy began to torn his clothes off and jack off vigorously. Joel immediately followed him and both guys were now naked and masturbating.
Randy shot his load first and lost balance of his new body so he fell over Joel and they fell inside the shower. With their bodies so close to each other, their dizziness and the water falling on them, Randy took his fat dick and rubbed it with Joel's. He put his lips on him and kissed him even more passionately than he did with Katy a minute ago.
Joel didn't fight against it and he began to hug their growing bodies, wet by the shower. When his hands met Randy's bigger fat ass he hold it firmly, feeling his brother's little hairs on it. They both were turning into hairy bears but he didn't care about it now.
Randy stopped kissing Joel for a second, their new beards were a little tangled. He realized that his little brother wasn't so little anymore, as he resembled a 30 year old guy and he must look the same. He blushed and tried to stand up but his new body that too foreign to him that he fell over his new fat ass. Joel took this opportunity to kiss him back and with his bigger manhood in hands, he united his fat dick tip with his brother's one. He stretched his long foreskin and sucked his brother's mushroom in a erotic dick docking. Randy can't resist it and quickly ejaculated in Joel's mushroom head, sharing his similar DNA with his now twin bear brother.
That last moment was the climax on their session and both guys fell in the ground panting for a moment before they fainted.