Once Jake made it into the kitchen, his mouth almost watered at the delicious smell of well cooked bacon. Jake saw Jesse shirtless in his boxers which displayed his 9 inch bulge quite well. Jake noticed Jesse was now sporting a solid pelt of chest hair which made its way down to his crotch - Jesse looked like a fully grown male stud of a man now, not the prepubescent younger brother that he was before. "Eat up bro, I'm saving some for after I work out. Are you gonna just hang at home and watch cartoons?" Jesse asked.
"I was thinking we both go to that fair in town. I heard it was really fun and cool" Jake replied, trying to convince his brother to agree.
"That sounds pretty sweet! I'll go shower and get dressed and then we can head out. Put some clothes on and watch tv while I get ready." Jesse said while he made his way upstairs to get ready.
"Perfect" Jake thought to himself. After a few minutes, he heard the shower turn on and Jake felt a bit curious as to how his brother's room changed. Jake made his way upstairs and snuck into his brother's room. Jesse's room now smelled almost like a locker room, a thick musk filled the air and clothes were strewn across the floor. "Wow he really is the bigger brother now" Jake thought. However, Jake noticed something odd - a pair of boxers he didn't remember owning before. "Weird, did Jesse buy new underwear for himself? This pair of boxers is too small for my...er his dick." Jake picked up the boxers and noticed they were a size suited for a young teen. Jake looked down and noticed he was still in his brother's old briefs, which looked childish. "Oh what the heck, I need to try to act more manly despite looking like a 13 year old." Jake said as he switched underwear, moving as quickly as possible so he wouldn't have to see his sorry 3 inch penis.
After Jake put the boxers on, he felt a strange warmth spread across his body. In a few seconds the feeling passed. "Weird" Jake said, not noticing his voice was slightly deeper. What Jake also didn't notice was the boxers accelerated his growth back to his original age of 18 - Jake now had faint wisps of armpit hair and thin hair around his ankles. Jake thought nothing of it and went to his room to get ready.