Bryan watched the scene slack-jawed. Don had just gone outside for a minute, and Bryan hadn't noticed his older brother disrobing. When dad had slammed the back door a minute ago, Bryan had jerked his head up to see the shocking display. His older brother was rolling around in some kind of plant, and dad, sporting a thick boner, was heading right for him. "Brett!" Bryan hissed.
Brett rushed over to the window just in time to see his dad spread open his robe and thrust his meaty cock into Don's up-ended asshole. Brett saw that Don had two fistfulls of shrinkweed and was smearing it all over his hairy chest. "Oh my god!" Brett exclaimed. "We have got to get them inside!"
Bryan nodded soundlessly, still overcome by the vision of hulkly homo lust that was unfolding in their yard. He heard Brett moving away, and turned to follow. Once his eyes were off his family members, Bryan had the presence of mind to ask, "Just how are we going to do that? Dad is built like a tank, and Don is quite a bit stronger than both of us." But Brett was already out the door so there was no reply.
The first thing Bryan noticed when he stepped outside was the smell. This plant gave off a sugary sweet odor, not a bad smell but a strong one. Probably an "acquired taste", as they say. Brett had already marched out to the scene and was saying something to dad, who was still standing behind Don and ramming his ass for all it was worth. Then Bryan noticed things looked a little different as he got closer. Dad's robe was already touching the ground, and Don's feet seemed a lot smaller and more delicate than the should have. Those were interesting observations, but Bryan also noticed his dick was getting hard, and that seemed a lot more important right now.
Brett, meanwhile, seemed totally unaffected. He had managed to get the plants out of Don'a hands somehow and was helping his oldest brother up off the ground. "Bryan!" Brett yelled. "Come grab a hold of Dad."
Bryan was starting to feel a little light headed, and by the time he reached dad, the man he had obeyed for so many years seemed small and, well, shrunken. As Brett managed to get Don standing on wobbly legs, Bryan saw his older brother had shrunk dramatically to only half his size. Wrapping his arms around dad's chest, Bryan saw it wasn't the thick, manly chest it should have been. It was still hairy and muscular, but it had the dimensions of a child's. As Bryan held on, it was clear that dad was still casting off his inches.
As Brett carted Don off towards the house, he called over his shoulder, "Come on! We've got to get them into the shower and wash this stuff off. Hurry!"
Bryan turned dad around slowly, his own mind cloudy. Dad was mumbling something, and he started to struggle. As his hunky father slipped below four feet, he had a moment of lucidity saying, "Bryan? Bryan? Is that you?" The struggling reduced, and Bryan was able to point dad back towards the house, but the small man still resisted leaving the yard.
"Yeah, Dad," Bryan answered, his tongue feeling thick and heavy. "I'm here, it's going to be ok. Let's get inside."
"Bryan, bless you." Dad replied with a sigh, and Bryan could swear he felt his father shrink and entire inch in his embrace. The older man put one hand on Bryan's much larger paw. The little fingers were not without strength, though, and Bryan felt his hand firmly guided into his dad's crotch and onto the rock-hard boner that stood at attention there, still a respectable size even after all the size that had been lost. "Can you give your old man a hand?" dad asked, now masturbating himself with Bryan's big hand.
Bryan, who was by now quite dizzy and overwhelmed by everything that was going on, grasped his father firmly and started stroking. Nothing else had made any sense so far this morning, but somehow everything had fallen into place once this hard cock was in his hand. "Yeah, sure dad," Bryan said, now hungrily feeling his father's small body, but enough of Bryan's sense remained to add, "Let's just get inside."
Dad nodded and together the pair staggered towards the door. Bryan could now hear his father's mumblings more clearly. Moaning was interspersed with, "oh fuck", and "yeah", "let me shrink!", and "smaller!". When the reached the house, Bryan shut the door with one hand, and quickly shed his father's robe, having grown from a robe to a cape and now a real inconvenience.