Breathing heavily after his orgasm with his new dick, Jeff grabbed some tissues to clean himself off. As he was wiping off his stomach, he suddenly had the urge to see if it tasted the same as his own cum. So he scooped some up with his finger and put it into his mouth. The taste was definitely different, and clearly his brother's cum, not his. This made him curious to see if his brother had even noticed the change and if he had, how he was reacting to it. Jeff gathered up his clothes from off the floor and slipped them on, noticing how his brother's junk fit differently in his pants. The sensations of having a new dick was making him hard again, even though he'd just came. He quietly opened up his door and walked quietly out into the hall.
Jacob's room was on the other side of the hall, and Jeff crept over to it. The door wasn't all the way closed so Jeff tried to peek inside. It looked empty, and Jeff couldn't hear anything in there, so he slowly opened the door and stepped inside of his brother's room. Looking around, Jeff saw a pretty average room for a 15 year old boy. Jacob didn't have any posters hanging on his walls, preferring them bare. Jacob's desk was messy, homework scattered on it in front of his own computer. On the other side of the room was his brothers bed, with his dresser at the foot of it. As he saw the dresser, Jeff became suddenly aware again of how his new junk didn't fit as well in his clothes. Closing the door of his brother's room, he slipped out of his pants and grabbed some of his brother's underwear. Jeff slid off his boxers and looked at his brother's briefs before sliding them on. Once he had them on, he felt much more comfortable. The new sensations on his groin made his dick, which had started to soften, get hard again. He gingerly touched it, then heard the downstairs door open and slam shut and someone running up the stairs.
In a hurry, startled Jeff grabbed his pants and dove underneath his brother's bed to hide. Shortly afterward, Jacob came running into the room and closed the door. From underneath the bed, Jeff saw his brother pull down his pants and stand in front of the full-body mirror on the back of his door. Jeff could see the reflection in the mirror and saw Jacob reach into his underwear and pull out his now much larger dick and balls and stare at them in the mirror. The image of a bigger dick on Jacob's frame turned Jeff on even more. Jacob played with it, getting harder himself as he watched his reflection.
Jacob glanced to the side and saw on the floor Jeff's abandoned boxer shorts. Jeff felt like an idiot for forgetting them. Jacob, however, reached down and picked them up and held them a moment before bringing them up to his face and taking a deep breath, inhaling their scent. Jeff saw his old cock on Jacob's body grow rock hard. After sniffing the boxers, Jacob took off his own underwear and put Jeff's on, admiring the way his brother's rock-hard cock looked in them. Jacob continued rubbing his new cock through the boxers.
Jeff couldn't help but be turned on, and felt his very stiff cock straining against the briefs he was wearing. He couldn't resist reaching down to rub it has he watched his brother begin to masturbate his own former cock through his own boxer briefs. As he moved, he accidentally knocked against a box, making a sound. He froze.