Ty smiled at his little sister, though calling her his little sister anymore was a bit of a joke. With her firm, round breasts on her chest, and her matured sexy face, she hardly looked like anything about her could be considered little anymore. In effect, he felt a little disturbed at the prospect of growing up his sister anymore, despite his innate curiosity about seeing what kind of woman she might turn out to be.
Ty smiled inwardly, however, when he realized that he could easily fix this situation. He silently wished for Dusty to admire herself in the mirror for a few minutes, and not notice him in the slightest. Dusty looked up from her step brother, confused momentarily, before walking over to the mirror, exploring her nude body with a strong curiosity. Ty stood up off the bed and wished another full bodied mirror into existence, while simultaneously taking off all of his clothes.
He stood in front of the mirror, an impressive looking specimen to say the least, and slowly began to age himself. His muscles began to grow more defined, and more sculpted, his abs turning into a solid hard 8 pack in the process. His body grew taller, inching upwards before stopping at a towering 6'6''. His jawline became more angular, and a light coating of hair covered his whole body. His penis, erect from the flood of testosterone flowing through it, also expanded, becoming a full eleven inches long. Ty let out a long, shuddered moan as his transformation into a well-hung, chiseled 20 year old was complete. Satisfied with what he saw, he went over to the bed and laid back down, willing Dusty to come away from the mirror and resume her pleading look at him. Of course, he altered history to make her think that he had always been 20.
"Please big brother," Dusty pleaded, unintentionally batting her eyes and sticking out her pouty bottom lip in a sexy fashion, "I want to be grown up like you!"
"I don't know," you said softly, "You may have to go a bit further than just jerking me off to grow up fully, sis." Mentally, he removed all of the compunctions a thirteen year old girl would have, mentally, towards the concept.
"But I really want to," Dusty said, "Maybe if I kiss your penis, I'll grow up?"
"It's worth a try," Ty replied, smiling. Dusty bounced off the bed and laid down in front of you, approaching this with a great deal of ethusiasm. With little trepidation she slowly lowered her lips onto Ty's penis and tentatively kissed it. When nothing happened, she gave it a much longer kiss, licking it with her tongue, causing Ty to moan in pleasure. Dusty looked down, disappointed that she had yet to grow any further.
"I think you're going to have to do more, sis." Ty said, smiling. "I think the only way to become a woman is to do what women do with men like me."
Dusty thought for a moment, before her eyes widened at realization of what he was saying. "You mean I have to..." When Ty nodded his head, she bit her bottom lip in thought. "But you're my step brother. Isn't there a law against it?"
"No..." Ty replied. "And you want to grow up all the way. This is the only way I think it will work." Dusty thought about it for a moment before Ty sat up and helped her lay down on the bed. "Just let me help you sis." Ty said in a gentle caring voice, "You'll like this." He leaned down and began to passionately kiss his sister, to which she responded in time. They continued to kiss with growing passion, before Ty looked up and smiled at his sister, while silently wishing that her hymen would magically disappear. When she nodded, he slowly sheathed his penis insider her, causing her to yelp at the alien sensation, and then moan in pleasure as he filled her fully.
"Oh my god Ty," she let out in a passionate, breathy voice, "This feels...it...it's indescribable." She looked down as Ty slowly began to slide in and out of her, and let out a shout of joy when she saw her breasts begin to grow ever so slowly. "It's working Ty!"
Ty could barely hear her now, overcome with the animalistic desire to fuck this woman and fuck her completely. As he increased his rhthym, pistoning in and out of her with increasing strength and velocity, Dusty's body grew more, filling out and completing its transformation into blonde bombshell. In a few minutes, both Ty and Dusty let out a simultaneous scream of ecstasy, Ty's seed spilling out and filling her now completed womb.
They both laid their, sweaty and overcome for a moment, before Dusty stood up and tentatively approached the mirror. She shakily extended a hand towards the mirror as she stared at the reflection of womanhood in front of her. Her breasts had grown to, compared to what they had been before, a gargantuan EE size cup. Her long blonde curls cascaded down her back, framing her seductive face in a halo of light.
"Thank you so much big brother," she replied to Ty, who merely stared up at the ceiling unresponsive...