"You know," Ty said, "I feel like the four of us should spend a little time alone to...'explore' our new bods."
Ky smiled at this, as did Dustin and Justin. The two pairs of conjoined siblings--four heads in all--wanted to get to know each other a little better.
"What about Mom and Dad?" Dustin asked. His parents June and Mark were still in the house--and even if Ty had wished that the four body bros' condition would be seen by others as normal, June and Mark would surely find it strange if their birth sons and foster sons acted and spoke as though they had only known each other for a few minutes.
To solve this problem, Ty used his power to make another wish. In a flash of light, the four brothers found themselves in a large white space, one that had no clear boundaries--they were obviously standing on some kind of soft floor or ground that went on forever, and they could see no visible walls or ceiling. There was a door some ten feet away, with a doorframe that stood with no wall.
"Where are we?" asked Justin.
"I teleported us into a new world," Ty explained. "This world exists outside many if not all of Earth's laws of physics, meaning that we can do anything we want to here."
"What about our family and friends back home?" Dustin asked.
"This world's timeline is a bit different from Earth's," Ty answered. "One minute there will basically be like a year or two here. This means that if we teleport back to Earth, hardly any time at all will have passed there, but we will still remember everything that happened here."
"Well, that's a bit of a relief," said Ky. "I guess this means we'll all be able to get to know each other for some time, and then after a while we can go back and successfully act as though me and Justin have always existed."
"But, before we start, what is that for?" Justin asked as he pointed to the door.
"It leads you to a separate area of this world," Ty explained. "It looks pretty much like this area we're in now, and I made it in case anyone wanted some space of their own. It's also soundproof in each space, and the door has a special lock in case someone REALLY needs privacy."
"Clever," Dustin smiled. "Were you and Ky thinking of starting by...(ahem) getting to know each other alone?"
Ty and Ky smiled and nodded in agreement. Both Dustin and Justin knew what they meant, and agreed to slip into the other space for a while to do the same. After squeezing through the door, Dustin waved to Ty and Ky as Justin shut the door. Once the lock clicked, Ty and Ky were ready to get started.
They started by slipping off their two-headed T-shirt, tossing it away so that it landed near the door. Next, they reached down to their waist and unbuckled the belt. After unzipping their jeans, they threw them and the belt onto the shirt to form a pile. This left the final barrier: the pair of underwear. They stretched the waistband from their skin, pulled it down towards their ankles, and out from underneath their two feet, after which the underwear was flung into the pile as well. The two body bros were now completely naked, and ready to start.
Ty made a bed appear behind them, and the two lay down on it to get comfortable. Ty then made all the things that turned him on appear before them: among these things were a hydra, various aliens from Ben 10, and several other things that had multiples of something--arms, legs, heads, etc., either alone or in various combinations. Slowly but surely, Ty and Ky's shared package began to grow. As it did, it gradually stiffened until it was sticking directly out from their shared body. As soon as the peak was achieved, one of the pair reached for it and began rubbing.