"Hey, Dad," Tyler says, smiling and looking down at you. "Like what you see?"
Your seven-foot tall son stands in front of you, completely nude. Your mouth hangs open, not believing your eyes. You see his bed has partially collapsed; that must be what the crashing sound had been. And, to top things off, Tyler's cock is fully hard now, jutting straight out from his crotch.
"T-Tyler!" you say, shaking your head incredulously, "what happened to you?"
Tyler shrugs. "I dunno. I just woke up this morning, horny as usual. I started whacking off, and I felt my body begin to expand a bit. Like this!"
He grasps his member, and you can see his body begin to inch even further upward. As he begins to stroke it, the growth accelerates and he leans his head back, his tongue hanging out of his mouth in pleasure.
"Tyler, what are you doing?!" you ask, your breathing rate increasing, partially out of fear and partially out of (you hate to admit it but it's true) lust. Tyler, however, ignores you, and he speeds up his beating off, his free hand moving across his chest, down his lean stomach, and, finally, grasping his balls, fondling them.
You are shocked by how big he is now, over nine feet tall and getting bigger. When his head starts to brush against the ceiling, he stops, letting go of his erection, which is dripping with pre-cum.
"Ahhh, that always feels great," Tyler says, "and the growth makes it even better!"
The scent from Tyler's pre fills your nostrils, and with the combination of seeing the stunning body of your giant, lean son in front of you and the pheromones in the air has made you grow aroused, and you try to hide your own excitement.