"I wanna be a stallion." Dustin gasps and almost cums when finishing the sentence, keeping his hand away from his twitching cock now.
"Like a feral or anthro one?" Ty yawns at the answer, always knew that his foster brother had a horse cock fetish or something.
"A-anthro of course! I still want to use my hands, you dork!" Dustin's body started to spasm, gaining a bit more muscle and height. "Wh-what's happeniinnning?!"
"I highly advise you not to call me anymore names, Dustin." Ty glares at his older brother, stepping close till he was right in his face. "I am GOD of this new world, and you will do your best to remember that."
"A-AH...M-My body!..It..It feels like it's on fire!" Dustin looks down and notices his cock swelling in size inch by inch, getting thicker and starts to turn into a darker color. "Nnnnngg! M-my cock!"
"Let's go somewhere more suitable for this." Ty said, wishing for them to be in a nice quiet pasture. The smell of fresh cut grass was relaxing to Ty, though the other teen was having his own experiences. "Now Dustin it's important to keep your humanity in check. It can be very easy to give in to your animal instincts."
"Uugghhh so gooood..." Dustin moans out stroking his 15 inch cock, now being 6 foot 3 and having short brown fur form all over his body. "A-AGH GOD I CAN FEEL IT HAPPENINNGGG!!" His face began to contort and expand, getting long to fit that of a horse. The bones in his feet crack and shifted into hooves, making him stomp hard after each one was formed. His cock became a true horsecock now, throbbing with a flared head as pre-cum shot out in a unusual large volume. Dustin lets out a very loud neigh as his transformation was finished with a nice, flowing mane. Dustin grunts and neighs some more as he furiously strokes his new cock, coming hard after a long minute of stroking to shoot what seemed like a gallon worth of cum onto the ground. "I need to..I need to breed something!" Dustin this sprints off, his new animal senses leading him to any nearby female.
"Oh well," Ty shrugs, taking a handful of cum in his hand to lick it up. "I warned him not to let go of his humanity..wonder who he will find to mate first?"