Ty smiled to himself. He'd wished for Dustin to become the girliest femboy in the world, with access to all manner of sex toys and an irresistible desire for cock, yet to stubbornly retain his self image of being straight. Dustin was deep in the closet, both literally and figuratively, but everyone who didn't think he was an actual girl would know he was gay as a rainbow.
Ty had given him some time to explore himself. Now to see if he'd managed to resist the urges. Ty barged into Dustin's room and caught his brother passionately riding a massive horse dildo and drooling. The girly looking boy's eyes went from half lidded to wide and panicking at being caught.
"Fucking yourself again, Dustin? You're such a fag," Ty said, triggering Dustin's denial mid self fuck.
"N... No! I... I'm not gay," he said, almost begging. He hadn't stopped bouncing up and down on the horse cock though. Actually, now that he was being watched, Dustin was picking up speed. Ty could see the struggle in the poor boys eyes as he tried and failed to stop himself.
Time to make this even worse / better for the fag. With a wish, the horse dildo because real. A portal connecting it to a real horse. And it began to grow harder and longer and thrust on its own.
Dustin cried out but still couldn't get off the expanding cock. Ty pushed Dustin back onto the bed, wishing that the portal was stuck right up against Dustin's ass and couldn't fall out.
The horse continued to pound Dustin vigorously. The bulge was clearly visible through the femboy's slim belly. Ty began to lick Dustin's sensation nipples. The boi squirmed and moaned under him.
"See, I told you, you are a fag."
"No! No! I'm straight! I'm... Ah!" Ty bit his nipple and twisted the other one. The horse began to ejaculate inside Dustin's ass. The boy screamed in pleasure, cuming onto himself with his pathetic excuse for a penis. Ty scooped up the cum and brought to Dustin's face. The fag began licking it up and sucking on Ty's cum covered fingers in between feeble protests against being gay.
Ty turned the horse cock portal into a horse cock plug instead, to keep all that horse cum sloshing inside his brother for a while.