Family Ties/Jump Off
You slide off your Daddy's lap and turn to face him. "It's not fair," you cry. "Timmy and I used to share everything, now he doesn't even want me to come in his room."
"That's because he's growing up too," he says. "Do you know what masturbation is?"
Blushing again, you nod. "I think so," you say. "Boys call it jerking off."
"Do you think Timmy might be jerking off in his room and would be embarrassed to be caught?"
"Uh! Oh! Maybe. I guess..."
"What about you? Have you tried it?" Your first instinct is to say no, but you find yourself nodding. You notice that the lump in his pants, which had subsided, has come back. Thinking about his penis makes you giggle.
"It's a lot easier for boys of course. Get hard, grab a hold and rub." he says.