Once given the green light, I couldn't resist the temptation. My straight brother, a twink with a tight, untouched ass, became my target. I started slow, stroking his cock until it was rock hard, then lubed up my massive dick and pressed it against his virgin hole. He tensed, but I whispered encouragement, and soon, I was sliding in, inch by inch. His eyes widened as he felt my size, but he didn't pull away. I fucked him slow and deep, letting him adjust, then picked up the pace, slamming my hips against his ass, making him moan.