You feel yourself up in your new body, turn around a couple times in your bed and then get out. "I believe you have something that's mine Jason." You say to your unconscious brother. You grin as you pull away his blanket. There he lays in Zack's Speedo and soccer shirt. You grab the Speedo with your new hands and slowly guide in down Jason's legs exposing his nice cock. You smile as you hold the Speedo in front of you. It is soaked by a combination of Jason's cum and sweat. "Hmmm." You lay down the Speedo on the bed and quickly take of Zack's pajamas. You pick the almost dripping Speedo back up and step into its holes with your legs. You pull up the Speedo leaving a trail of the mixture behind on your legs. Arriving at your crotch area you put the Speedo right where it belongs. "A perfect fit." You walk around a bit to make the mixture spread around your waist and dick. You feel a ring of moist within the Speedo.
You walk back over to Jason and start pulling his shirt off. "Luckily he's still unconscious" you think. "This would have really woken him up." You take off his shirt and you own pajama shirt. You smell the soccer shirt as you hold it in front of you. You put the shirt on and are slowly being covered with drops of Jason's sweat. You walk around in the room a bit to make sure you're entirely covered. You then grab your member and swipe it across the Speedo's fabric. You start to pump your young cock using Jason's mixture as lubricant. "Hmmm." The pleasure starts to run through your body. You sit yourself down on the floor and spread your legs. You guide your free fingers to your virgin asshole and start to invade it. "Unggg" you softly moan as your cock starts to add his own juices to the Speedo's mixture. "C'mon Zack. You can do this" you say to yourself as you put another finger up your ass.
You then come up with an idea. Since Jason has given you a nice and soaked Speedo to enjoy, you have to give him something in return. You stand up pulling all your fingers out of your ass at once and walk over to Jason's closet. There you grab his clean underpants and you take if your Speedo. You put on Jason's underpants and put on your Speedo on top of it. Right at the moment you have put your Speedo into place you are overwhelmed with pleasure. Cum quickly fills the underpants up and your semen starts to flow into the Speedo. To make sure Jason's gets his deserved amount of cum, you rub your borrowed hand over your Speedo, causing it to mix up its with mixture of cum with the fresh semen in the underpants. "Perfect" you say as you completely soaked the underpants.
To finish it off you take both your pants off and walk over to Jason. There you put his legs into the holes of his cleanly soaked underpants and slide the pants up his legs. Before wrapping it around his crotch you quickly give a good squeeze in your big brother's naked, sticky balls. You smile satisfied and wrap the underpants around his waist. "There" you say as put your own wet Speedo back on. Now that you have rewarded Jason well, you think about what you can do next.