"Okay, fine." Dustin sighed heavily. "It's not like I can stop you anyway. Test away, I guess."
"That's the spirit!" Ty grinned, approaching his now dwindled step brother. It was astounding how Ty now stood a few inches taller than Dustin. His adoptive brother had always towered over him, a mass of athletic muscle, and now he had deflated down to a short and skinny pre-teen body. Dustin's eyes widened with fear as Ty placed a slim hand on his shoulder. "Look at you. So small and cute. Hardly the big buff jock anymore."
"Uh, Ty..." Dustin gulped gently, his mouth going dry from nervousness. "W-What are you doing?" Dustin felt a deep homophobic revulsion, but didn't dare object lest Ty alter him.
"Shhh..." Ty whispered gently. "You like boys too, remember?"
"Uh, yeah, of course." Dustin blushed suddenly, confused as a sudden bi-curious urge rose up in him. He was so small and helpless before Ty, and... he liked it? "B-But you're my brother!"
"Step brother." Ty corrected with a smirk. "And besides, it's just me and you." Ty emphasized his point by placing his hand over Dustin's crotch gently, watching the other boy blush deeper. "Nobody has to know."
"K-Kiss me?" Dustin gulped, aching for the warmth of his brother's lips as he felt himself starting to grow aroused. Ty complied only willingly, and before long both boys were held in a warm embrace, caressing each other as they made out. Ty was thrilled with how tender and meek Dustin was being, and almost laughed at his fabled reputation for being a rough lover in high school. If his pussy hungry jock buddies could see him now.
After a time, Ty drew away to find his pants tented obscenely. Dustin, though much smaller, was no less flagged after their encounter. Ty said nothing, implied nothing, and began loosening Dustin's already loose pants. He dropped them to no objection and was met with a small penis barely the length of an index finger. At this, Dustin blushed even redder and seemed shamed. "I-I used to be a lot bigger before you shrank me."
"That's okay." Ty reassured him, grinning. It'll be enough for what I have in mind." He began removing his own clothes to reveal a quite a bit more substantial five inches. Not terribly thick, but average for his size.
Dustin averted his gaze for only a moment, his residual homophobia dying away to curiosity. "Can I touch it?"
"Of course." Ty smiled, and sat on the floor. Now Dustin, in only a baggy t-shirt, began touching the first cock besides his own, rubbing tiny smooth hands on what seemed to be an enormous member, gently gripping and stroking it, urging Ty to grow harder. "That's really nice." Ty gasped. "But I want more."
"So do I." Dustin gulped. "What..." Realization set in and he suddenly understood why Ty had wanted him small. "Do... Do you want me to fuck you?"
"I'd like that." Ty blushed now, startled as Dustin vocalized his desire.
"Yeah. I'd like that too." The smaller step brother grinned, his little cock throbbing.